CHAPTER XXV.
The Roentgen or X-Rays.

The majority of people have been accustomed to regard light as something to be excluded and controlled by opaque screens just as effectively as rain is excluded by a tin roof, or cold is kept out by a brick wall. The shady retreat furnished relief from the garish day to the primitive man, and the opaque shades and Venetian blinds of modern civilization exclude the excess of light at our windows. Sunshine and shadow have, in fact, been correlated conditions to the ordinary observation of man since time began. The last few years of the Nineteenth Century, however, were to witness the discovery of a new kind of light ray which, in its behavior, subverted all previous conception of the nature and action of light. It was a species of electric light, which we are accustomed to regard as brilliant, but this light ray was invisible to the eye. It could not be refracted or bent from its course by a prism or lens, and it was so subtle, penetrating and insidious, that it could not be barred out like sunlight, but passed readily through many opaque substances, such as wood, flesh tissue, paper (even a book of 1,000 pages), as well as some of the metals. The lighter the weight of the substance, or less its density, the easier these rays passed through it, or the more transparent such bodies were to the rays. The heavier metals, like platinum, gold and lead, were practically opaque, or allowed none of the rays to pass through them, while the very light metal aluminum was about as transparent to these rays as was glass to ordinary light, and for that reason this metal could form window panes for such rays, while excluding other light. Most organic substances are transparent or semi-transparent to these rays, and hence such rays readily pass through the body of an individual, being only intercepted in part by the denser parts of the anatomy, such as the bones, so that a man in such light no longer casts a well-defined shadow of his outline, but the shadow disclosed is that of a skeleton, by virtue of the greater density of the bones. Any object of higher density, such as a ring upon the finger, clearly establishes its shadow by virtue of its greater density. Likewise, any foreign object in the body, such as a bullet from a gun-shot wound, or a foreign body accidentally swallowed, is perfectly disclosed and located by the shadow which it casts. As these light rays have been characterized as invisible, it may be difficult to understand how invisible rays can cast a visible shadow, and it should be here stated that when these unseen rays fall upon certain chemical substances the latter are made to glow with a peculiar fluorescence, and a screen made of such fluorescing materials will light up where the rays fall upon it, and remain dark at the points where the rays are intercepted by a substance opaque to such rays, thus outlining a shadow.

Not only do these light rays in passing through the body tissues (transparent to them) cast a shadow of the bones or any foreign objects, but by the application of photography to these shadow pictures a species of photograph, called a radiograph, or skiagraph, may be taken, and thus any foreign body, such as a bullet, may be definitely located in the human body and quickly extracted, without the element of doubt which beset the old method of diagnosis, which, at best, was only intelligent guessing. Not only are foreign bodies so located, but the fractures of the bones may also be accurately observed, studied and adjusted. Stone in the bladder may be discovered, and the condition and movements of the heart and lungs ascertained.

This new kind of light ray was discovered November 8, 1895, by Prof. W. C. Roentgen, of the Royal University of Wurzburg, and was named by him the “X-Ray,” probably because the letter x in algebraic formula represents the unknown quantity, and the hitherto unknown and elusive quality of this light suggested to Prof. Roentgen this appropriate name.

As before stated, a peculiar quality of the X-Rays is that they are not visible to the eye. A beam of X-Rays, thrown into a dark chamber through an aluminum window, would produce no illumination whatever in the room, but such rays would still penetrate the room, and if a fluorescing screen were placed in their path it would instantly light up. It is not surprising, therefore, that these subtle rays should have so long eluded the observation of the scientist.

A brief sketch of the conditions leading up to the discovery of the rays is necessary to a proper understanding of the same.

Every student of physics remembers the old-time lecture room experiments in which the Geissler tubes, with their beautiful play of colored lights, illustrated the action of the electrical discharge from the glass plate machine or the Ruhmkorff coil, on rarified gaseous media. Electrical experiments in high vacua by Sir William Crookes, and by Hittorf and Lenard, have greatly added to the present knowledge in this field, and paved the way to the discovery of Prof. Roentgen. It was known that a vacuum tube, variously called after the names of these scientists, as a Crookes, Hittorf, or Lenard tube, having platinum electrodes sealed in its ends, would, under the static discharge of electricity through it, give peculiar manifestations of light. One of the conducting terminals of such tubes was called, in electrical parlance, the “anode,” from the Greek ανα (up) ὁδος (way), meaning the way up or into the tube, and referring to the entering path of an electric current, or its positive pole; while the other was called the “cathode,” from κατα (down), ὁδος (way), meaning the way down or out, and referring to the outgoing path of an electric current, or its negative pole. When such glass tube, partially exhausted of air, received through its anode and cathode terminals a discharge of static electricity, a peculiar manifestation of light is seen between the anode and cathode terminals. At the anode it appears as a peach blossom glow, and at the cathode it appears as a bluish green light. If the exhaustion of the air in the tube is carried very high, approaching a perfect vacuum, or to about one millionth of the atmospheric pressure, the glow light at the anode disappears, and that at the cathode increases until it fills the entire tube with its characteristic light. This is called the “cathode ray,” or “cathodic ray,” an illustration of which is given in Fig. 215, where the cathode ray is seen in a Crookes tube emanating from the negative pole N or cathode a, and casting a shadow of the Maltese cross b into the end of the tube, as seen at d. Many of the characteristics of the cathode ray had been observed prior to Prof. Roentgen’s discovery, which, briefly stated, grew out of the following observation: He noticed that when a vacuum tube illumined by the cathode ray was completely masked or covered up by an external shield of black paper, so that no illumination of the tube was visible to the eye, there still passed through it certain subtle rays of light, invisible to the eye, but which would instantly illuminate a sheet of paper coated on one side with barium platino-cyanide, even at a distance of two yards or more, and that these invisible light rays were capable of passing through many substances opaque to ordinary light. He also discovered that these rays could be made to take a shadow photograph on a sensitive plate without even exposing the plate in the usual way, the X-Rays passing freely through the opaque ebonite or pasteboard screen of the plate holder. It did not take the scientific world long to realize the immense importance of this discovery, and to-day X-Ray apparatus constitutes the greatest addition to the surgeon’s resources that has ever been made in the form of mechanical appliances, since by its aid any foreign body in the human frame of greater density than the flesh may be at once definitely located and extracted, or any fracture of the bone disclosed, as the case may be. In the illustration, Fig. 216, is shown an X-Ray photograph of the hand of a gentleman whose thumb bone has been destroyed by disease.

Soon after the announcement of Prof. Roentgen’s discovery, apparatus was devised for seeing with the naked eye the image formed by the shadow of the X-Rays. Prof. Salvioni constructed such a device and described it before the Rome Medical Society as early as February 8, 1896. He called it the “cryptoscope.” It was quite a simple affair, and consisted of an observation tube with a lens, having in front of it a screen of fluorescing material, such as platino-cyanide of barium. When the object to be examined, the hand, for instance, was held in front of the fluorescing screen, and the X-Rays from the vacuum tube fell upon the hand, located between the vacuum tube and the fluorescing screen, a shadow of the bones was cast on the fluorescing screen by virtue of the greater density of the bones, which shadow was clearly discernible to the eye at the end of the observation tube. By this device one was able to see his own bones through the flesh. A device, invented by Edison and called the “fluoroscope,” was constructed on substantially the same principle. This used a tapered observation tube like the old-fashioned stereoscope box, which had at its outer wide end the fluorescing screen, and its small end fashioned to fit the forehead and strapped thereto so as to enclose both eyes. This device is shown in Fig. 217, in which an X-Ray vacuum tube is housed in a wooden box, on which the hand of the patient, or other part to be viewed, is laid, the X-Rays passing readily through the top of the box and casting a shadow of the bones of the hand, or foreign body, on the fluorescing screen of the observation tube. Edison’s experiments also led him in constructing his fluorescing screen, after testing a great number of substances, to select the chemical known as calcium tungstate, instead of the barium platino-cyanide, since the calcium tungstate appeared to give better results in fluorescing. Many other chemicals can be used, however, for making the fluorescing screen, such as the sulphides of calcium, barium and strontium. A recently discovered and powerful fluorescing substance is the double fluoride of ammonium and uranium, discovered by Dr. Mecklebeke. Such fluorescing materials are spread in a thin layer on the side of the screen next to the observer in the viewing apparatus.

It is not to be understood that such viewing apparatus is necessary in taking a surgical photograph. In such case only the X-Ray tube, means for exciting it, the patient’s body, and the sensitive photographic plate, are essential factors, the patient’s limb or body being interposed between the light tube and photographic plate, so as to cause the X-Rays emanating from the tube to cast the shadow of the patient’s bones, the bullet in his body, or other foreign object, directly upon the photographic plate, the sensitive and conscious plate obeying the will of these subtle rays, and receiving the impress of their actinic effect under conditions which it denies to ordinary light.

For exciting the vacuum tube any electrical machine capable of throwing a series of sparks across a gap of about five inches is sufficient. Various electrical machines may be used for this purpose, the Holtz, or the Wimshurst glass plate machine, the Ruhmkorff, or induction coil, or even the high frequency transformer. A good example of a complete X-Ray apparatus is that in use at the Army Medical Museum at Washington, made by Otis Clapp & Son, and shown in Fig. 218. The electrical generator is of the Wimshurst type, and is shown in a large glass-enclosed cabinet on the right. The glass disks within are rotated either by a small electric motor shown on the floor, or by a hand crank above. The X-Ray tube, of globular or bulb shape, is shown just above the patient’s hip, and its opposite poles are connected by wires to the opposite electrodes of the generator. When the current is switched on by the operator, the bulb is illuminated with the cathode rays, and the X-Rays, proceeding therefrom through the clothing and flesh of the patient, cast a shadow of the patient’s hip joint upon the photographic plate placed on the cot beneath the patient.

In the effort to secure greater sharpness in the image cast by the X-Rays, various forms of vacuum tubes have been devised. That shown in Fig. 219 represents one of the most important improvements. K is the cathode plate, formed of a concave disk of aluminum, which focuses the rays at a point near the center of the bulb. At this point a plate of platinum A, which metal allows practically none of the X-Rays to pass through it, is mounted on the anode in such an angular position that it gathers the focused rays and reflects them through the side of the tube. They thus make a sharper shadow than when radiating from the more extended surface of the glass.

In Fig. 220 is shown an X-Ray tube, as applied for locating a foreign body in the brain cavity, in which view the patient’s head is interposed between the X-Ray tube and the fluorescing screen, or photographic plate, as the case may be; while Fig. 221 shows the application of the same devices to the body. In both these views the particular form of X-Ray apparatus is known as the “Fluorometer,” made under the Dennis Patent, No. 581,540, April 27, 1897, and it is devised with reference to more accurately locating the foreign object by its shadow, for which purpose adjustable bracket-sights, seen in Fig. 221 on opposite sides of the body, are provided for bringing the X-Rays into proper alignment for projecting the shadow of the foreign body in true indicative position on the fluorescing screen, while a cross hatched grating behind the body, graduated in aliquot spaces of an inch, furnishes a measured field, and forms an easy and quick means of platting the position of said object. In the position of parts in the two figures the horizontal line, on which the foreign object lies, would be determined, but it would not indicate how deep in the object was, i. e., whether it was in the middle, or on one side. To determine this the fluorescing screen and grating are placed under the patient, and the X-Ray tube above, and the vertical line of the object is thus obtained. Both the vertical line and horizontal line having been obtained, it will be obvious that the foreign object will lie at the intersection of these two lines, which establishes for the surgeon its definite location.

It has been observed by Prof. Elihu Thomson, and also by Dr. Kolle, that the X-Rays are not absorbed and destroyed by the sensitive chemicals of a single photographic plate, but so potent and penetrating is their influence that the rays pass through and produce an image on a number of plates, placed one behind the other, thus affording means for multiplying the image at one exposure.

Among other uses of the X-Ray may be mentioned its capacity to detect spurious from genuine gems, the diamond giving a distinct color from its imitations, as do also most other precious stones.

A peculiar physiological effect of the X-Rays is their capacity to produce a severe effect on the skin, somewhat resembling sunburn. Such result, produced by long and continued exposure, has sometimes so deranged the skin tissues as to make sores that resulted in the entire loss of and renewal of the skin.

The discovery of the X-Ray by Prof. Roentgen may be fairly considered one of the most wonderful scientific achievements of the century, and his first memoir in 1895 is so full, clear and exact, as to have left very little more to be said about it. It is to-day, as it was found by him in 1895, the same mysterious, unseen, but positive force, a species of electrical energy without a domicile, and needing no conductor, a form of light passing through closed doors, invisible itself, and yet lighting up certain substances with a halo of glory, and radically changing and decomposing others. Rivaling the sun in actinic power, and writing its autograph with an unseen hand, it is truly called the X-, or unknown, ray.

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CHAPTER XXVI.
Gas Lighting.

For many centuries the going down of the sun marked a cessation of man’s labors, and among his first efforts toward increasing his efficiency was the prolongation of his hours of vision by artificial illumination. Beginning with a shell for a lamp, a rush for a wick, and the fat of his game for oil, the first crude lamp was made, and while it shed but a feeble and flickering light, man ceased to go to sleep with the fowls and the beasts, and continued his labors and amusements into the night. For many centuries the lamp held its exclusive sway, and probably will ever find a useful place; but with the discovery of coal gas and its practical manufacture the nights of the Nineteenth Century have been made to represent illuminated illustrations of the world’s progress. Coal gas can hardly be claimed as an invention, however, for natural gas from the bowels of the earth had been observed and used in China from time immemorial. The holy fires of Baku on the shores of the Caspian and elsewhere were also thus supplied. The first steps toward its artificial production began in the latter part of the Seventeenth Century with Dr. Clayton. Bishop Watson, in 1750, and Lord Dundonald, in 1786, also experimented with combustible gas made from coal, but the man who more than any other contributed to its practical manufacture and introduction was Mr. Murdoch, of Redruth, Cornwall, England. In 1792 Murdoch erected a gas distilling apparatus, and lighted his house and offices by gas distributed through service pipes. In 1798 he so lighted the steam engine works of Boulton & Watt, at Soho, near Birmingham; and in 1802 made public illumination of the works by this means on the occasion of a public celebration. In 1801 Le Bon, of Paris, used a gas made from wood for lighting his house. In 1803-4 Frederick Albert Winsor lighted the Lyceum Theatre, took out a British patent No. 2,764, of 1804, for lighting streets by gas, and established the National Light and Heat Company, which was the first gas company. In 1804-5 Murdoch lighted the cotton factory of Phillips & Lee at Manchester, the light being estimated as equal to 3,000 candles, and this was the largest undertaking up to that date. In 1807 Winsor lighted one side of Pall Mall, London, and this was the first street lighting. A disastrous explosion occurred shortly afterwards, and such eminent men as Sir Humphrey Davy, Wollaston, and Watt expressed the opinion that it could not be safely used; but the so-called “coal smoke” had come to stay, and in 1813 Westminster Bridge and the Houses of Parliament were lighted with gas. In 1815 there was general adoption of gas in the streets of London, and shortly afterwards in Paris. In 1805-6 David Melville, of Newport, R. I., invented a gas apparatus and lighted his house with it. He took out United States patent March 18, 1813, and in 1817 contracted with the United States to supply for a year the Beaver Tail Lighthouse. In 1815 James McMurtrie proposed the lighting of the streets of Philadelphia; Baltimore commenced the use of gas in 1816, Boston in 1822, and New York in 1825.

In Fig. 222 is shown a diagrammatic illustration of the principal features of a gas works, as employed throughout the greater part of the Nineteenth Century. On the left is seen the furnace, in which is arranged above the fire a series of retorts, which are in the nature of horizontal closed cast iron boxes. Only one of the series is visible in the view. Their ends project out beyond the furnace walls, and have doors for giving access to the interior, and each retort outside the furnace is connected by an upright pipe to an elevated cylinder called a hydraulic main. When the retort is charged with coal through its end door, and is heated red hot by the subjacent fire of the furnace, a heavy gas is driven off from the coal, which passes up the pipe to the hydraulic main, where it partially condenses and leaves its heavier portions in the form of coal tar and ammoniacal liquor. The gas then passes through the series of bent pipes, which form a condenser, where other remaining portions of the tar and other impurities are condensed, and drawn off from time to time in the little well shown on the left of the coil. From the condenser coils the gas passes into the purifier, shown on the right of the coils as an enclosed case having a series of shelves on which is spread slaked lime, which takes up from the gas impurities in the form of sulphuretted hydrogen and carbonic acid. From this purifier the gas passes downwardly through a pipe into a large gas holder whose lower end is sealed in a water tank, and which gas holder is balanced by weights and chains passing over pulleys. With the gas holder, the distributing mains of the city are made to connect to receive their supply. When the gas holder is full it is buoyed up by the lighter gas, and occupies an elevated position, and as its supply is used up, the gas holder settles down into the water.

In the operation of gas making many valuable secondary products are formed. The coal in the retorts is not entirely consumed, but is reduced to the condition of coke, and in this form is sold for fuel. The ammoniacal condensations are purified to form ammonia, while the coal tar, which but a few years ago was little more than a waste material, is now a valuable commercial product, being extensively used in the manufacture of the aniline, phenol, and naphthalene dyes, also in medicines and perfumes, and being used in crude form also as an important element in street paving compositions.

Water Gas.—In 1875 an important era in gas making was inaugurated by the introduction of what is known as “water gas,” so called for the reason that water in the form of steam is decomposed and its hydrogen, mixed with carbonic oxide gas, is mingled with a heavier carbon gas from oil, and is converted at a high temperature into a permanent, stable illuminating gas, at a much lower cost than coal gas.

Fontana was the first to notice the decomposition of steam by incandescent carbon to form hydrogen and carbonic oxide. Ibbetson’s British patent, No. 4,954, of 1824, represents the first application of this principle. This was followed by Alexander Selligue, who, in 1834, obtained a French patent, No. 9,800, and in 1842 produced water gas at Batignolles, a suburb of Paris. Sanders’ United States patent, 21,027, July 27, 1858, was the basis of an experiment tried at the Girard House in Philadelphia. These, with Siemens’ British patents, Nos. 2,861, of 1856, and 972, of 1863, for methods of constructing furnaces, constitute the earlier steps in the development of water gas, although many other patents were granted prior to the latter date for various methods and forms of apparatus. The practical production and successful commercial use of water gas, however, began with T. S. C. Lowe, who obtained United States patent No. 167,847, September 21, 1875, and revolutionized the gas making industry. In less than a dozen years from the date of his patent 150 cities and towns in the United States were using water gas, and in 1886 the Franklin Institute gave to Mr. Lowe a grand medal of honor for his invention, which of those exhibited that year was believed to contribute most to the welfare of mankind by cheapening the cost of light. Fig. 223 represents an illustration of the Lowe apparatus as shown in his patent, and whose operation is as follows: Valves 9 and 10 being open, an anthracite coal fire in generator chamber 1 gives off carbonic oxide gas, which passes down pipe 2 and enters the base of superheater 3, where mixing with air coming down pipe 4, it burns to form an intense heat. The chamber, 3, is filled with loose pieces of fire brick, which are soon heated white hot. Valves 9 and 10 are then closed and steam is taken from an upright boiler, 6, and carried by a small pipe, 7, to the incandescent mass in chamber 3, and passing down through it is superheated. This superheated steam passes from the bottom of chamber 3 to the bottom of chamber 1, and then up through the mass of red hot coal. The intensely hot steam is thus decomposed into hydrogen and oxygen, and the oxygen unites with the carbon of the coal to form carbonic oxide gas. As hydrogen and carbonic oxide burn with only a feeble blue flame, these gases are now made richer in light giving carbon at this point by the addition of oil contained in an elevated tank, 8. This, dripping on the incandescent coal in chamber 1, is volatilized, and at the same time enriches and combines with the hydrogen and carbonic oxide to form a permanent illuminating gas (water gas) that passes up pipe 5 and through the flues in boiler 6, to outlet 13, and thence on in the usual way to the condenser, scrubber and gas holder, which are not shown, and merely act to purify the gas. As the excessively hot water gas passes through the boiler flues it furnishes the necessary heat to generate the steam. The air used in the process is forced at 12 into a drum in the smokestack, 11, and is heated by the escaping products of combustion. In practical operation there are two (or more) of the steam superheating chambers 3, working alternately, and one of them is being heated up while the other is superheating the steam.

Water gas has neither the illuminating nor the heating qualities of coal gas, and it is also much more poisonous. According to O. Wyss, one-tenth of 1 per cent. of uncarburetted water gas renders the air of a room injurious to health, and 1 per cent. is fatal to all warm-blooded animals. Notwithstanding these facts, however, its extreme cheapness and fairly satisfactory light have carried it into such general use that to-day it is said that two-thirds of all gas made in the United States is carburetted water gas.

Acetylene Gas is a combination of two parts carbon and two parts hydrogen. It was discovered in 1836 by Edmond Davy, who produced carburet of potassium, and evolved acetylene gas therefrom by decomposing it with water. It was long known as klumene, and when burned it produced an intense white light. For a long time it was only produced in a small way in the laboratory. It is now made commercially by the mutual decomposition of water and calcium carbide, the latter giving off, when brought in contact with the water, acetylene gas, which rises in bubbles. In the reaction the carbon of the carbide unites with a portion of the hydrogen of the water, producing acetylene gas (C₂H₂), while the calcium of the carbide unites with the oxygen of the water and the remaining portion of the hydrogen and forms calcium hydrate, or slaked lime, which precipitates as a slush.

The union of carbon with an alkali metal, first accomplished by Davy in 1836, was followed in 1861 by the combination of carbon with calcium by Wohler. It was not, however, until the electrical furnace became an agency in chemical reaction that calcium carbide was made on a commercial scale. The production of acetylene gas for illuminating purposes began with the operations of Thomas L. Willson in 1893, and his patents, Nos. 541,137 and 541,138, of June 18, 1895, and 563,527 and 563,528 of July 7, 1896, cover the chemical process, the product, and the mode of operating. The reaction is a very simple one. A mixture of lime and carbon is subjected to the heat of an electric arc, and the carbon combines with the calcium of the lime to form calcium carbide, which appears on the market as dirty black stone-like lumps. The simplicity of the method of generating acetylene gas from this substance by merely bringing it in contact with water has greatly stimulated invention in this field. The art began practically in 1895, and since that time more than 500 patents have been granted for acetylene gas apparatus.

A very simple apparatus for the purpose is shown in Fig. 224, in which a vessel containing water has an inverted bell or cylinder within it, open at its lower end. A basket or cage is suspended within the inner cylinder, and contains a few lumps of calcium carbide, which are first immersed in the water by being forced down by the rod supporting the same, which passes through a stuffing box. Acetylene gas is immediately generated and its pressure forces the level of the water down in the inner cylinder, causing it to rise in the annular space between said cylinder and the case. As the water level descends in the inner chamber it passes out of contact with the calcium carbide, and the generation of gas is discontinued until some of the gas is drawn off or consumed at the burners, whose pipe is shown connecting with the gas space of the inner cylinder. When so drawn off, the pressure in the inner cylinder is relieved, and the water therein rises to contact again with the calcium carbide and renews the generation of gas. This principle of automatic action is a very old one, and will be recognized by the student as that of the Dobereiner lamp of the chemical laboratory, invented by Prof. Dobereiner, of Jena, in 1824.

In acetylene gas apparatus a great variety of methods are employed for bringing the water and carbide into contact. Instead of the automatic pressure level principle described, many devices discharge a regulated quantity of powdered calcium carbide into the water, while in another form the water is discharged upon the calcium carbide. An example of the latter is given in Fig. 225, which represents the Criterion generator. A number of receptacles containing charges of calcium carbide are made to successively receive a regulated quantity of water, the gas being collected in a rising and falling holder.

Acetylene gas finds its principal uses for isolated plants, and in country houses. One form of using it is to compress it under high tension in cylinders, but this method has been attended with some disastrous explosions, and is discriminated against by the insurance companies.

Calcium carbide is now made in a large way by the Willson Aluminum Company, at Spray, N. C., and also at Niagara Falls and at Sault St. Marie, Mich., and its cost is between 3 and 4 cents per pound.

Acetylene gas has an acrid, garlicy odor, and burns with an intensely white flame, and so superior is it to coal gas in illuminating power that it only requires a pipe of one-third the diameter of that used for coal gas to produce the same illuminating effect.

Carburetted Air is another form of illuminating gas which has found some useful applications. This consists simply of air forced through some light hydrocarbon, such as naphtha, benzine or gasoline, and so saturated with the vapors of these volatile substances as to become an inflammable mixture. Many patents have been granted for apparatus operating on this principle, and it has been put to some practical use in country houses, and seaside resorts.

Pintsch Gas is another special application. It is a gas made from oil and compressed in storage cylinders by means of pumps for portable use. It is stored under a pressure sometimes as high as 150 pounds to the inch, its pressure being reduced at the burners through the agency of pressure regulators. It is used for lighting railway cars, buoys, and lightships.

Gas making has probably been the most extensive and important of all the commercial chemical operations of the Nineteenth Century, and with it has come a great array of minor inventions as accessories. Among these first came the gas meter and pressure regulator. With the introduction of gas into houses some means of determining the amount consumed as a basis of payment was required, and for this purpose the gas meter was devised. The first gas meters were known as wet meters, and effected a measurement by passing the gas through a liquid and rotating a wheel therein. The wet meter was invented by Clegg (British patent No. 3,968, of 1815), and the dry meter, by Malam (British patent No. 4,458, of 1820), and improved by Defries (British patent. No. 7,705, of 1838). The gas regulator is simply a little automatic apparatus whereby the variation of pressure in the gas main is reduced and the flow rendered perfectly uniform at the burner. It effects a saving of gas by preventing it from blowing when the pressure is too great, and also gives a more steady and uniform light.

Among the great number of mechanical devices which have grown out of the use of gas may be mentioned the gas range for heat, the gas engine for power, and the Welsbach burner for light. The gas range has contributed much to the domestic economy of the city house. It gives an immediate heat in the kitchen for all culinary and domestic purposes, without the incidental objections of having to transport fuel and remove ashes. It is put into or out of action in an instant, saves labor and time, and avoids the heat and discomfort of a coal stove during the hot months of summer. It is organized in principle after the Bunsen burner, whereby a perfect combustion of the carbon is obtained with maximum heating effect and without smoke or deposits of lampblack.

The Otto gas engine, seen in Fig. 226, is a pioneer and representative type of a great number of explosive gas engines, which in recent years have become active competitors of the steam engine where only small power is required. The Otto engine is covered by patent No. 194,047, August 14, 1877. Patents No. 222,467, 297,329, 336,505, 358,796, 320,285, 386,211 and 549,160 represent important developments in this art.

The Welsbach burner for improving the quality of gaslight, and economizing its consumption, is also well and favorably known. It utilizes the Bunsen burner principle to make a very perfect combustion of the gas, with the greatest possible heat and the least smoke, and then directs its great heat on to a refractory body which will not burn, but glows with a brilliant white incandescence. The Welsbach burner was brought out in 1885. The United States patent therefor was granted October 7, 1890, to Carl Auer Von Welsbach, No. 438,125. The Welsbach light is a development of the Drummond, or limelight, invented by Lieut. Drummond, of England, in 1826. This latter exposed a piece of quick lime to the intensely hot flame of the oxy-hydrogen blow pipe, which was invented by Dr. Robt. Hare in 1802. The piece of lime glows with an intense brilliancy approximating that of the electric light. The Welsbach burner, see Fig. 227, operates on the same general principle, except that the refractory body, which is heated to incandescence, is a tubular sleeve of netted fabric first steeped in a solution of the salts of refractory earths, and then incinerated by heat to burn out the textile fibre and leave the refractory earthy oxides as a skeleton of the fabric, and which is called a “mantle.” This mantle is suspended above the flame arising from a proper admixture of air and gas, and is heated thereby to a brilliant incandescence which furnishes the light. In the Welsbach burner the light seen does not proceed directly from the combustion of the gas, but from the white hot mantle. The light is a very pure white one, does not distort or falsify colors, and effects a great saving of gas. An important improvement upon the mantle is covered by Rawson’s patent, July 30, 1889, No. 407,963, for coating the mantles with paraffine or analogous material to toughen them and prevent them from breaking in packing and transportation.

Natural Gas.—No review of gas lighting would be complete without some reference to the development incident to the use of the natural gas flowing from the internal reservoirs of the earth. Such gas has been known and utilized for centuries in China, and was conveyed by the Chinese in bamboo pipes to points of utilization. The discovery of coal oil in the United States in 1859, and the great advances made in the methods and apparatus for sinking oil wells, have resulted in the discovery of numerous wells of natural gas, whose values were quickly perceived and utilized by their owners. The village of Fredonia, N. Y., was probably the first to be lighted by natural gas, and a flow from a well at West Bloomfield, N. Y., opened in 1865, was carried in a wooden main more than twenty miles to the city of Rochester. Many wells of natural gas have since been found at various points, and so extensive has been its use for cooking, heating, lighting and metallurgical processes, that thousands of patents have been taken for various forms of burners, pressure regulators and other appliances for utilizing the same. The annual production of natural gas in the United States for 1888 was valued at $22,629,875. There has, however, been a steady decrease in the past ten years. The amount produced in 1897 was $13,826,422. The insatiable demands of modern civilization must some day exhaust the supply, and what will take place when the subterranean chambers are relieved of their burden is a question for the geologists to answer.

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CHAPTER XXVII.
Civil Engineering.

Almost entirely of an outdoor character, and necessarily on public exhibition, the engineering achievements of the Nineteenth Century have always been conspicuously in evidence, challenging the admiration of the public eye. They represent man’s attack upon the obstacles presented by nature to his irrepressible spirit of progress. Difficulties apparently insuperable have confronted him, only to melt away under his persistent genius until nothing seems impossible. He has connected continents with the telegraph, has crosshatched the land with railroads, penetrated the bowels of the earth with artesian wells, opened communication between oceans with the Suez Canal, reclaimed territory from the sea in Holland, pierced mountain ranges with tunnels, drained marshes, irrigated deserts, reared lofty structures of masonry and steel, spanned waters with magnificent bridges, opened channel-ways to the sea, built beacons for the mariner, and breakwaters for the storm beaten ship.

Probably the most important branch of engineering work is railroad construction, already considered under steam railways. Closely related to the railroad, however, is bridge building, and many of these noble structures hang between heaven and earth, conspicuous monuments of the engineer’s skill.

The Forth Bridge.—This massive structure, of the cantilever type, is shown in Fig. 228. It was begun in 1882 and finished in 1890, and is the largest and most costly viaduct in the world. It is built across the Firth of Forth, and is the most important link in the direct railway communication of the North British Railway, and associated roads, between Edinburgh on the one side, and Perth and Dundee on the other. The total length of the viaduct is 8,296 feet, or nearly 1⁵⁄₈ miles. The extreme height of the structure is 361 feet above the water level, and the foundations extend 91 feet below the water level. The two main spans are 1,710 feet, and these both give a clear headway for navigation of 150 feet height. There are over 50,000 tons of steel in the superstructure, and about 140,000 cubic yards of masonry and concrete in the foundation piers. The three main piers consist each of a group of four masonry columns faced with granite, 49 feet in diameter at the top, and 36 feet high, which rest on solid rock, or on concrete carried down in most cases by means of caissons of a maximum diameter of 70 feet to rock or boulder clay.

No intelligent conception of the enormous size of this great structure can be obtained except by comparison. Estimating from the bottom of the masonry piers to the towering heights of the cantilevers, it reaches above the dome of St. Peter’s at Rome, and is only a little short of the height of the greatest of the pyramids of Egypt. The cost of the bridge is given as £3,250,000 or nearly $16,000,000.

The Brooklyn Bridge.—Having for its successful construction and maintenance the same foundation principle upon which the spider builds its web, this magnificent bridge of steel wires spans the East River between New York and Brooklyn, with a total length of 5,989 feet, and in length of span and cost is second only to the great Forth Bridge. It is shown in Fig. 229, and among suspension bridges it ranks first. It has a central span of 1,595¹⁄₂ feet between the two towers, over which the suspension cables are hung, and has a clear headway beneath of 135 feet. It has two side spans of 930 feet each between the towers and the shore.

The suspension towers stand on two piers founded in the river on solid rock at depths of 78 and 45 feet below high water, and they rise 277 feet above the same level. There are four suspension cables 15¹⁄₂ inches in diameter, each composed of 5,282 galvanized steel wires, placed side by side, without any twist, and arranged in groups of 19 strands bound up with wire. These cables have a dip in the center of the large span of 128 feet, rest on movable saddles on the top of the towers to allow for slight movement of the cables due to expansion and contraction, and are held down at the shore ends by massive anchorages of masonry. The bridge has a width of 85 feet, and has two roadways, two lines of railway, and a foot way. It was begun in 1876 and opened for traffic in 1883, and its cost was about $15,000,000. It fulfills a great function for the busy metropolis, and it hangs in the air a monument in steel wire to the genius of the Roeblings.

Masonry Bridges.—The largest and finest single span of masonry in America, and believed to be the largest in the world, is to be found about 9 miles northwest of the city of Washington. It is known as the Washington Aqueduct or Cabin John Bridge, and is seen in Fig. 230. It extends across the small stream known as Cabin John Creek, and carries an aqueduct 9 feet in diameter, that supplies the National Capital with water, its upper surface above the water conduit being formed into a fine roadway. It is 450 feet long. Its span is 220 feet, the height of the roadway above the bed of the stream is 100 feet, and the width of the structure is 20 feet 4 inches. Gen. Montgomery C. Meigs was the engineer in charge of its construction. It was begun in 1857 and finished in 1864, with the exception of the parapet walls of the roadway, which were added in 1872-3. Its cost was $254,000. Only one other masonry arch has ever been built which equalled this in size. The Trezzo Bridge, built in the fourteenth century, over the Adda in North Italy, and subsequently destroyed, is said to have had a span of 251 feet, but the Washington Aqueduct Bridge at Cabin John is a noble work in masonry, and when standing beneath its majestic sweep, and viewing the regular courses of masonry hanging nearly a hundred feet high in the air, and springing more than a hundred feet from the embankment upon either side, one loses sight of the principles of the arch, and the fear that the mass may fall upon him gives way to the impression that nature has bowed to the genius of man, and suspended the law of gravity.

Among the patents granted for bridges the most important are those relating to the cantilever type, among which may be mentioned those to Bender, Latrobe, and Smith, No. 141,310, July 29, 1873; Eads, No. 142,378 to 142,382, September 2, 1873, and Clarke, No. 504,559, September 5, 1893.

Caissons.—For submarine explorations the ancient diving bell, which was said to have been used more than 2,000 years ago, has given place to diving armor, while for more extensive local work the pneumatic caisson is employed. The latter was invented by M. Triger, a French engineer, in 1841. An early example of it is also given in Cochrane’s British patent No. 3,226, of 1861. It consists of a vertical cylinder divided into compartments, its lower open end resting on the river bottom. Compressed air forced into the lower compartment forces the water back, while the men are at work, the intermediate chamber forming an air lock, by which entrance to, or egress from, the lower working chamber is obtained. The pneumatic caissons of Eads (patents Nos. 123,002, January 23, 1872, and 123,685, February 13, 1872) and Flad (patent No. 303,830, August 19, 1884) are modern applications of the same principle. The sinking of shafts through quicksand, by artificially freezing the same and then treating it as solid material, is an ingenious modern method shown in patents to Poetsch, No. 300,891, June 24, 1884; and Smith, No. 371,389, October 11, 1887.

Tunnels.—Less conspicuous than bridges, by virtue of their underground character, but none the less important, are these mole-like means of communication. Especially difficult of construction for the reason that the nature of the soil or rock is largely unknown, and for the reason also that the work may have to encounter faults in rocks, and springs or quicksands in the earth; nevertheless the demands of the railroads for shortening the distance of travel and economizing time have stimulated the engineer to expend millions of dollars in piercing the earth with these great underground passageways.

The Mont Cenis Tunnel was constructed to establish railway communication between France and Italy through the Alps. It was begun in 1857, and after having been in progress of construction for thirteen years, was opened for traffic in 1871. This tunnel was commenced by hand borings, being for the most part through solid rock, and its progress up to 1862 was so slow that it was estimated that thirty years would be required for its construction. Its earlier completion was due to the introduction of rock drills operated by compressed air, which trebled the rate of advance, and which device made a new epoch in all rock-boring and mining operations. This tunnel was cut from both ends at the same time, and so accurate were the surveys in establishing the alignment of the two headings through the mountain mass, that, although the tunnel was more than 7¹⁄₂ miles long, when the two headings came together in the middle, only a difference of one foot in level existed between them. When it is remembered that most of the 7¹⁄₂ miles of tunnel was cut through solid rock, by boring and blasting, the immensity of the undertaking can be appreciated. As completed the tunnel is 8 miles long, and wide enough for a double track railway.

The St. Gothard Tunnel is another tunnel through the Alps, which involved even a longer and deeper cut through the mountains than the Mont Cenis Tunnel. This is 9¹⁄₄ miles long, and it was begun in 1872, the headings joined in 1880, and the tunnel opened for traffic in 1882. Although by far the largest undertaking yet made, the improvement in rock-boring machinery enabled it to be constructed much more rapidly and at less expense.

The Arlberg is still another Alpine tunnel. It is 6¹⁄₂ miles long, was commenced in 1880, and opened for traffic in 1884.

Tunneling under rivers presents many more difficulties than driving through the hardest rock. This is so by reason of the inflow of water. Among successful tunnels of this kind may be named the Mersey and Severn tunnels in England, opened in 1886, and the St. Clair tunnel between the United States and Canada. The histories of the abandoned Detroit and Hudson river tunnels are object lessons of the difficulties encountered in this class of work.

An important engineering invention for tunneling through silt or soft soil is the so-called “shield.” This was first employed by the engineer Brunel in the construction of the Thames tunnel, which was begun in 1825 and opened as a thoroughfare in 1843. The shield, as now used, is a sort of a cylinder or sleeve as large as the tunnel, which sleeve, as the excavation proceeds in front of it, is forced ahead to act both as a ring-shaped cutter and a protection to the workmen, its advance being effected by powerful hydraulic jacks or screws which find a back bearing against the completed wall of the tunnel. As the digging proceeds the shield is advanced, and a section of tunnel is built behind it which, in turn, furnishes a bearing for the jacks in the further advance of the shield.

This latter improvement was the invention of the late Alfred E. Beach, of the Scientific American, and was covered by him in patent No. 91,071, June 8, 1869, and was used in driving the experimental pneumatic subway constructed by him under Broadway, New York, in 1868-9, and also in the St. Clair River tunnel and the unfinished Hudson River tunnel and other works.

Subsequent improvements made upon the shield by J. H. Greathead of England and covered by him in United States patents Nos. 360,959, April 12, 1887; and 432,871, July 22, 1890, have greatly added to the value and efficiency of this device, and made it one of the leading instrumentalities in tunnel construction.

Suez Canal.—It is said that the undertaking of connecting the Mediterranean and Red Seas was considered as long ago as the time of Herodotus, and a small channel appears to have been opened twenty-five centuries ago, but was subsequently abandoned. In 1847 the subject was again taken up for serious consideration, the work begun in 1860, and finished in 1869, at a cost of £20,500,000, or more than a hundred million dollars. The canal starts at Port Said, on the Mediterranean, a view of which with its ships of all nations and the canal reaching far away in the distance is seen in Fig. 231. The canal extends nearly due south to Suez on the Red Sea, a distance of about 100 miles, through barren wastes of sand and an occasional lake. It was originally formed with a bottom width of 72 feet, spreading out to 196 to 328 feet at the top, and of a depth of 26 feet, but has since been increased in transverse dimension to accommodate the great increase in travel.

Sixty great dredges were employed on the work, and the dredged material was discharged in chutes on to the bank. The canal was the work of M. De Lesseps, the eminent French engineer, and has proved a great success from both an engineering and financial standpoint. The stock is mainly held in England, having been bought from the Khedive of Egypt. In 1898 the ships passing through the canal during the year reached the remarkable number of 3,503. The rate of tolls is 10 francs (about $2) per net ton. The gross tonnage of ships passing through in 1898 was 12,962,632, the net tonnage 9,238,603. The total receipts for the year were 87,906,255 francs (about $17,500,000), and the net profit 63,441,987 francs (about $12,500,000). An average size ocean liner pays about $5,000 for the privilege of sailing through this great ditch. Admiral Dewey’s ship, the “Olympia,” returning from the Philippines, paid for her toll $3,516.04, and the “Chicago,” $3,165.95. Going the other way, our supply ship “Alexander” paid $4,107.99, while the “Glacier” paid $5,052.38. Ships making the passage through the canal move slowly on account of the washing of the banks, about 22 hours being required, but the shortening of the travel of ships going east and west, and the saving of life, property, and time, involved in avoiding the circuitous and stormy passage around the Cape of Good Hope, has been of incalculable benefit to the world.

With the construction of canals and harbors, great improvements have been made in dredges. Some of these are of the clam-shell type, some employ the scoop and lever, others an endless series of buckets. An example of the latter, used on the Panama Canal, is seen in Fig. 232. Still another form, and the most recent if not the most important is the hydraulic dredger, which, by rotating cutters, stirs and cuts the mud and silt, and by powerful suction pumps and immense tubes draws up the semi-fluid mass and sends it to suitable points of discharge. The best known of the latter type is the Bowers hydraulic dredge, covered by many patents, of which Nos. 318,859 and 318,860, May 26, 1885; 388,253, August 21, 1888; and 484,763, October 18, 1892, are the most important.

For surface excavations in solid earth the Lidgerwood Cableway is an important and labor saving device. A track cable is stretched from two distant towers, and a bucket holding well on to a ton of earth is made to travel on a trolley running on said cable track, rising at one end out of the excavation, and dumping at the other end to fill in the excavation as the cutting progresses, all in a continuous and economical manner. This device is made under the patent to M. W. Locke, No. 295,776, March 25, 1884, and comprehends many subsequent improvements patented by Miller, Delaney, North and others. The Chicago Drainage Canal is a work just completed, which largely employed these devices. This canal was designed to connect the Chicago River with the Mississippi River, so as to send the sewage of Chicago down the Mississippi instead of into Lake Michigan. Although it cost $33,000,000 and required seven years for completion, the labor-saving cableways greatly cheapened its cost and shortened the time of its construction.

Among the leading inventions relating to canal construction may be mentioned the bear-trap canal-lock gate (patents Nos. 229,682, 236,488 and 552,063), and the Dutton pneumatic lift locks. The latter provide ease and rapidity of action by a principle of balancing locks in pairs, and are covered by his patent No. 457,528, August 11, 1891, and others of subsequent date.

Artesian Wells represent an important branch of engineering work, and they are so called from the province of Artois, in France, where they have for a long time been in use. Extending several thousand feet into the subterranean chambers of the earth, they have brought abundant water supply to the surface all over the world, from the desert sands of Sahara to the hotels of the modern city; they have contributed oil and gas in incredible quantities to supply light and heat, and have made valuable additions to the salt supply of the world.

They are driven by reciprocating a ponderous chisel-shaped drill within an iron tube, six inches more or less in diameter, which is built up in sections, and moved down as the cutting descends. The drill is reciprocated by a suspending rope from machinery in a derrick, and in order to give a hammer-like blow to the chisel a pair of ponderous iron links coupled together like those of a chain, and called a “drill jar” connect the drill to the rope. As the sections of the link slide over each other they come together with a hammer blow at the moment of lifting that dislodges the drill from the rock, and on the descending movement they come together with a hammering blow immediately after the drill touches the rock to drive it into the same. The first United States patent for a drill jar is that to Morris, No. 2,243, September 4, 1841. When an oil well ceases to flow, it is rejuvenated by being “shot,” which is quite contrary to the ordinary conception of prolonging life. For this purpose a dynamite cartridge is exploded at the lower end of the well, which shatters the rock, and, in opening up new channels of flow for the oil, renews the yield. Many patented inventions have been made in the field of well boring, and the discovery of coal oil in the United States in 1859 has developed a great industry and built up enormous fortunes. The amount of petroleum produced in the United States in 1896 was 60,960,361 barrels, the largest yield on record. In 1897 the amount was 60,568,081 barrels.

Of less consequence than the artesian well, but finding many useful applications, is the drive well. A metal tube with a perforated lower end is driven down by hammers into the ground, and furnishes a quick and cheap source of water supply. This was invented by Col. Green in 1861, in meeting the necessities of his military camp during the civil war, and was patented by him January 14, 1868, No. 73,425.

Rock Drills.—In mining and tunneling through rock, the rock drill has been the implement of paramount importance and utility. For boring by rotary action the diamond drill is most effective. This uses bits set with diamonds which, by their extreme hardness, cut through the most refractory rock with great rapidity. It was invented by Hermann and patented by him in France, June 3, 1854.

More important, however, is the compressed air rock drill, in which a piston has the drill bit directly on its piston rod and cuts by a reciprocating action. The piston is actuated by compressed air admitted alternately to its opposite sides in an automatic manner by valves. The compressed air conveyed to the drill in the tunnel or mine not only operates the drill, but helps to ventilate the tunnel. As early as 1849 Clarke and Motley, in England, invented a machine drill, and in 1851 Fowle devised a similar machine, having the drill attached directly to the piston cross head. The Hoosac and Mont Cenis tunnels greatly stimulated invention in this field, and among the notable drills of this class may be named the Burleigh, Ingersoll, and Sergeant. The Burleigh drill was brought out in 1866, and was covered by patents Nos. 52,960, 52,961 and 59,960 of that year, and 113,850 of 1871, and the Ingersoll drill, by patents No. 112,254, and No. 120,279, of 1871.

Blasting.—The discovery of nitro-glycerine in 1846, followed by its convenient commercial preparation in the form of dynamite, gave a great impetus to blasting. Notable as the largest operation of the kind in the century is the blowing up of Flood Rock, in the path of commerce between New York City and Long Island Sound. The dangerous character of this and other rocks in this vicinity gave long ago to this channel the significant name of Hell Gate. The undermining of the rocks by shafts and galleries is seen in Fig. 233, and the final blowing up of the same in a single blast was the culmination of a series of similar operations at this point tending to safer navigation. On October 10, 1885, 40,000 cartridges, containing 75,000 pounds of dynamite and 240,000 pounds of rack-a-rock, were, by the touching of a button and the closing of an electric circuit, simultaneously exploded. In the twinkling of an eye nine acres of solid rock were shattered into fragments by the prodigious force, and a vast upheaval of water 1,400 feet long, 800 feet wide, and 200 feet high, sprang into the air in tangled and gigantic fountains. As the termination of the most stupendous piece of engineering of the kind the world has ever seen, and with spectacular features fitting the enormous expense of $1,000,000, which the work cost, this final scene put an end to the menaces of Flood Rock, and wiped out of existence the worst dangers of Hell Gate.

Mississippi Jetties.—The broad bar and shallow waters at the mouth of the Mississippi involved such an obstruction to commerce that in 1872 it received the attention of Congress, resulting in the building, by Capt. Eads, of the celebrated jetties. They were begun in 1875 and finished in 1879, and cost $5,250,000. The channel obtained was 30 feet deep and 200 feet wide. Its construction involved the building across the bar and out into the Gulf of Mexico two long reaches of parallel embankments, called jetties. This was effected by sinking mattresses of willow branches bound together and weighted with stone. These were laid in four layers, and when submerged, and resting upon the bottom, were covered with a layer of loose stone, and this in turn was surmounted with a capping of concrete blocks, as seen in cross section in Fig. 234. These jetties so concentrated the flow of waters into a narrow channel as to cause its increased velocity to wash out the mud and silt and deepen the channel. The immensity of the work may be measured by the quantity of material used in its construction, which included 6,000,000 cubic yards of willow mattresses, 1,000,000 cubic yards of stone, 13,000,000 feet (board measure) of lumber, and 8,000,000 cubic yards of concrete. The mattresses were laid 35 to 50 feet wide at the bottom, which width was considerably increased by the superimposed layer of stone, and the jetties extended 2¹⁄₄ miles into the sea. Their influence upon commerce is indicated by the fact that before their construction the annual grain export from New Orleans was less than half a million bushels, and in 1880, the year following their completion, it was increased to 14,000,000 bushels.

High Buildings.—A distinct feature of modern architecture is the enormously tall steel frame building known as the “sky scraper.” The increasing value of city lots first brought about the vertical extension of buildings to a greater number of stories, and the necessity for making them fireproof, coupled with the desire to avoid loss of interior space, due to thick walls at the base, made a demand for a different style of architecture. To meet this a skeleton frame of steel is bolted together in unitary structure, the floors being all carried on the steel frame, and the outer masonry walls being relatively thin, and carrying only their own weight. In Fig. 235 is shown an example of the interior structure of such a building. The vertical columns are erected upon a very firm foundation, and to them are bolted, on the floor levels, horizontal I-beams and girders, stayed by tie rods, which I-beams receive between them hollow fireproof tile to form the floor. The outer masonry walls are built around the skeleton frame, as seen in Fig. 236, and the details of connections for the floor members appear in Fig. 237.

Steel frame enclosed in masonry work

FIG. 236.—ENCLOSURE OF STEEL FRAME BY MASONRY.

Detail of steel frame construction

FIG. 237.—DETAILS OF INTERNAL CONSTRUCTION.

The construction of iron buildings began about the middle of the century. In 1845 Peter Cooper erected the largest rolling mill at that time in the United States for making railroad iron, and at this mill wrought iron beams for fireproof buildings were first rolled. In the building of the Cooper Institute in New York City in 1857 he was the first to employ such beams with brick arches to support the floors. The unifying of the iron work into an integral skeleton frame, for relieving the side walls of the weight of the floors is, however, a comparatively recent development, and this has so raised the height of the modern office building as to cause it to impress the observer as an obelisk rather than a place of habitation. An earthquake-proof steel palace for the Crown Prince of Japan is one of the modern applications of steel in architecture. It is being built by American engineers, and is to cost $3,000,000.

Eiffel Tower.—Loftiest among the high structures of the world, and significant as indicating the possibilities of iron construction, the Eiffel Tower of the Paris Exposition of 1889 was a distinct achievement in the engineering world. It is seen in Fig. 238. It is 984 feet high, and 410 feet across its foundation, and has a supporting base of four independent lattice work piers. In the top was constructed a scientific laboratory surmounted by a lantern containing a powerful electric light. The total weight of iron in the structure is about 7,000 tons, the weight of the rivets alone being 450 tons, and the total number of them 2,500,000. The level of the first story is marked by a bold frieze, on the panels of which, around all four faces, were inscribed in gigantic letters of gold the names of the famous Frenchmen of the century. The summit of the tower was reached by staircases containing 1,793 steps, and by hydraulic elevators running in four stages. The cost of this structure was nearly $1,000,000.

Washington’s Monument.—Next in height to the Eiffel Tower, and being, in fact, the tallest masonry structure in the world, this noble obelisk, by its simplicity, boldness and solidity, challenges the admiration of every visitor, and gratifies the pride of every patriot. It is seen in Fig. 239, and is 555 feet 5¹⁄₂ inches high, 55 feet square at the base, and 34 feet square at the top. The walls are 15 feet thick at the base, and 18 inches at the top, and its summit is reached by an internal winding staircase and a central elevator. At the height of 504 feet the walls are pierced with port holes, from which a magnificent view is had of the capital city and surrounding country. The summit is crowned with a cap of aluminum, inscribed Laus Deo. The foundation of rock and cement is 36 feet deep and 126 feet square, and the total cost of the monument was $1,300,000. The corner stone was laid in 1848. In 1855 the work was discontinued at the height of 152 feet, from lack of funds. In 1878 it was resumed by appropriation from Congress, and completed and dedicated in 1885, under the direction of Col. Thomas L. Casey, of the United States Corps of Engineers.

The Capitol Building.—Representing the heart of the great American Republic, and overlooking its Capital City, this grand building, shown in Fig. 240, is a poem in architecture. Massive, symmetrical and harmonious, its highest point reaches 307¹⁄₂ feet above the plaza on the east. It is 751 feet 4 inches long, 350 feet wide, and the walls of the building proper cover 3¹⁄₂ acres. Crowning the center of the building is the imposing dome of iron, surmounted by a lantern, and above this is the bronze statue of Freedom, 19 feet 6 inches high, and weighing 14,985 pounds, the latter being set in place December 2, 1863. The dome is 135 feet 5 inches in diameter at the base, and the open space of the rotunda within is 96 feet in diameter and 180 feet high.

The corner stone of the original building was laid in 1793 by Washington. The first session of Congress held there was in 1800, while the building was still incomplete. The original building was finished in 1811. In 1814 it was partly burned by the British. In 1815 reconstruction was begun, and completed in 1827. In 1850 Congress passed an act authorizing the extension of the Capitol, which resulted in the building of the north and south wings, containing the present Senate Chamber and Hall of the House of Representatives. The corner stones of the extension were laid by President Fillmore in 1851, Daniel Webster being the orator of the occasion, and the wings were finished in 1867. Since this time handsome additions in the shape of marble terraces on the west front have added greatly to the beauty and apparent size of the building.

It is not possible to give anything like an adequate review of the engineering inventions and achievements of the Nineteenth Century in a single chapter, and only the most noteworthy have been mentioned. The modern life of the world, however, has been replete with the resourceful expedients of the engineer, and the ingenious instrumentalities invented by him to carry out his plans. There have been about 1,000 patents granted for bridges, about 2,500 for excavating apparatus, and about 1,500 for hydraulic engineering. In mining the safety-lamp of Sir Humphrey Davy, in 1815, has been followed by stamp mills, rock-drills, derricks, and hoisting and lowering apparatus, and lately by hydraulic mining apparatus, by which a stream of water under high pressure is made to wash away a mountain side. Apparatus for loading and unloading, pneumatic conveyors, great systems of irrigation, lighthouses, breakwaters, pile drivers, dry-docks, ship railways, road-making apparatus, fire escapes, fireproof buildings, water towers, and filtration plants have been devised, constructed and utilized. Many gigantic schemes, already begun, still await successful completion, among which may be named the draining of the Zuyder Zee, the Siberian railway, the Panama and Nicaraguan Canals, the Simplon tunnel, the new East River Bridge, and the Rapid Transit Tunnel under New York City; while a bridge or tunnel across the English Channel, a ship canal for France, connecting the Bay of Biscay with the Mediterranean, a tunnel under the Straits of Gibraltar, and a ship canal connecting the great lakes with the Gulf of Mexico, are among the possible achievements which challenge the engineer of the Twentieth Century.

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