Taking a tape line, Fred sent the Italian to the other end of it, and they picked out a favourable location to measure across, making it over 11 feet at the narrowest spot from one edge to the other. Allowance was then made for bearings five feet on either side of the span, so that timbers 21 feet long would be required to cross the chasm. This width would require three string-pieces, or chords, to run across, one on each side, and one in the centre. These, covered with three-inch plank from end to end, would make a good, solid deck sufficient for all purposes. The planks were cut off seven feet long, to have the deck of the bridge, over all, exactly seven feet wide.

Among the timbers taken from the old barn were nine pieces, measuring 22 feet in length, 8 × 10 inches in section, so Fred decided to make use of three of these just as they were, without cutting, and to place them on their edges to get the most strength out of them. He then had six posts cut off the old cedar fence posts, about two feet long, which were sunk into the ground their whole length, as shown in Fig. 18, three on each side of the creek, and the tops made level, so that a flat timber or plank would rest on them, touching each one. This plank was made nine feet long, so as to project over the posts about a foot at each end. This was, of course, the same at each end of the bridge. After the flat timbers had been laid on the ends of the posts and fastened with spikes, there were laid the three long timbers spanning the gully. The spaces between were equally divided, and then covered with three-inch planks taken from the floor of the old barn. The boards were cut off to the proper length and fastened down on the three timbers with spikes five inches long, the planks not laid close together, but kept about three-eighths of an inch apart, in order to let the water run off after a rain, as well as to allow air to circulate underneath and between the joints to prevent the planks from decay.

In order to make the bridge safe, it was necessary to build a rail on each side. Two pieces of timber about 20 feet long and 6 × 6 inches square were used for the rails, while posts and braces were made of timber of about the same dimensions. The bottoms of the posts were halved, so that they could be spiked or nailed to the long outside string-pieces, as shown in the illustration. Tenons were made on the top of these posts, and these fitted into mortises made in the top rails, and all were then put together and fastened with wooden pins.

Nick dug away the surplus earth from the approaches to the bridge, and made an easy grade to its deck. This completed the work all but the painting, which was left to be done some other day.

Mr. Gregg inspected the bridge, pronounced it all right, and congratulated Fred on his workmanship, at the same time saying a good word to Nick and George, both of whom had helped very much to make the effort a success.

In the evening Mr. Gregg told Fred and George that a friend of his had given him a copy of the rules to be observed when running a launch, so he asked the boys to get their note-books, and take these down as he read them out. Even Jessie, too, he thought, ought to be acquainted with the rules, as she might be called upon some time to make use of them, so three pencils were soon at work, as the father read out the following:

• "1. When at the wheel, remember as a first consideration, that you cannot entertain the boat's occupants as well as steer.
• "2. Keep your course, and know what that course is.
• "3. Regulate your speed to the company you are in. Marine motors are, as a rule, very flexible.
• "4. Do not cut corners.
• "5. When approaching a landing, learn to judge exactly the distance your boat will travel after your propeller has stopped, so as to run alongside without using your reverse gear. This requires some practice, but is amply rewarded by time saved, in the long run, and decrease of wear and tear on engine, gear, and propeller. Any one can get to a landing in time by alternately running full speed ahead and then astern.
• "6. When aboard your boat, and facing the bow your right hand is starboard, your left, port. Keep to the right. Should you be overtaking any one, it is your duty to pass clear on their left. The above applies only to narrow waters.
• "7. When going up or down stream, should you wish to cross over to the other side and return, and another boat is overtaking you on your left, don't attempt to cross its bow; slow down until it has passed.
• "8. Keep clear of non-engined crafts. You have greater freedom of action than they; it costs you nothing, and their occupants appreciate your courtesy.
• "9. Do not tow canoes or skiffs alongside. If towed at all, they should be right aft with as short a towline as possible.
• "10. Finally; remember the rules of the road—
• "'Green to green or red to red Perfect safety—go ahead If to starboard red appear 'Tis your duty to keep clear. When upon your port is seen A steamer's starboard light of green, There's not so much for you to do As green to port keeps clear of you.'"

The children all promised to memorize these rules.

As the stuff for the boat was not expected for some days, Fred and Nick kept at work about the new boat house, and building up the landing dock. The former fitted up a work bench, and put his little shop in readiness for actual use. Fred also hunted for a nice stick of timber among the old barn ruins, on which to set up the boat. A good piece found, he cut it to a length of 20 feet, and then he and Nick got it into the boat house, where Fred planed it off a little with a rough jack plane, keeping a sharp lookout for nails, sand, or gravel. Nothing destroys the cutting edges of tools more than nails, bits of iron, glass, sand, or small pebbles, which sometimes escape the vigilance of the workman. Especially is this true of saws, which Fred knew quite well since he had once run a good sharp saw against a nail, while cutting a piece of timber in two. This taught him a lesson he never forgot, and whenever he had to cut up old material, he was always careful to examine it all round, and to scrape or brush off all the dirt and sand from the parts through which the saw teeth had to travel. In planing, or "dressing" the stick of timber, the same precautions were taken, and the surface of the wood was made as clean and free from dirt and sand as it possibly could be. Notwithstanding all this, Fred found it almost impossible to keep the cutting iron of his jack plane sharp enough to take off shavings. He had to sharpen it every few minutes. This is nearly always the case when working up wood which has previously been used. However, he managed to "dress" his stick very nicely, and after finishing it, laid it down along the middle of the floor of the shop, putting blocks of wood under it here and there to raise it up from the floor five or six inches. It was then made level on top and fastened down so that it would not move or get out of line. This was about all they could do on the boat until the materials arrived. Nick had managed to fill in the space between the two walls of the little pier with heavy bowlders, and had strengthened the whole with coarse rubble-stone work in such a manner that there was little danger of injury from floating ice or flood tides; and he had covered the whole over with small stones, gravel, and a good thick layer of cement concrete, which made it correspond with the cement walk.

The question of a winch was then taken up with Mr. Gregg and it was decided to construct a simple affair at the end of the boat-house opposite the large doors, where the boat would have to enter.

Mr. Gregg suggested, in order to make the end of the building strong enough, that two upright posts be set up, well braced by being fastened to both floor and ceiling, and that the winch be attached to them in a way that would be easy to work, as shown in Fig. 19, room enough being left between the posts and the wall for the crank to turn without the hand of the operator striking the boards. The cylinder around which the rope should wind ought to be about six inches in diameter, and the crank or handle on the end, not less than fifteen or sixteen inches long. The longer the crank, the less force it would require to haul in the boat. If desired, a crank could be fitted to the other end of the cylinder so that two persons could work at one time, pulling in the weight.

In the evening Mr. Gregg asked the boys and Jessie to visit his room, and he would try to explain the principle and advantages of the wheel and axle, as the winch they were to make was in a measure related to that principle. Mr. Gregg began by saying: "The wheel and axle is merely a modification of the lever and consists of a couple of cylinders turning on a common axis, the larger cylinder is usually called the wheel, the lesser one the axle. This arrangement, which I draw on the blackboard herewith, forms a kind of lever of the first or second class. Considered as a lever, the fulcrum is at the common axis, while the arms of the lever are the radii of the wheel and of the axle.

"The fulcrum is at C, the centre. The arm of the weight is W W, and the arm of the power is A C. In Fig. 20 the arm of the power is the spoke of the wheel, while the arm of the weight is the radius of the axle. Fig. 19 shows the ordinary winch, often used in well-digging for hauling up dirt and rock, and also for raising planks, shingles, rafters, and other light stuff, to the roofs and upper floors of buildings. Often it is made more powerful by adding spur or geared wheels to the end of the shaft, consisting of a pinion and a larger spurred wheel. The crank or handle is attached to the pinion, and the power is increased according to the difference in diameters of the spur wheels. The machine is then called a 'crab' and it is often used for lifting safes and other heavy weights to elevated situations. In Fig. 20 the length of the crank (in a straight line) is the arm of the power.

"The mechanical advantage of the wheel and axle equals the ratio between the diameter of the wheel and of the axle.

"It is not necessary that an entire wheel be present. In the case of the windlass and the capstan (Fig. 21), the power may be applied to a single arm or to a number of arms placed in the holes shown. The cable or rope on the barrel of the capstan is hauled in by turning the capstan on its axis, with handspikes or bars. The capstan is prevented from turning back by a pawl attached to its lower part, working in a circular ratchet on the base.

"As an illustration of the lever action, and of work put into and got out of a machine, there is no better illustration than the ingenious contrivance termed the fusee (Fig. 22). In good watches and clocks, where the elastic force of a coiled spring is used to drive the works, the fusee compensates the gradually diminishing pull of the uncoiling spring. The driving of the works at a constant rate is the object for which a watch or clock is designed. This usually entails a constant resistance to be overcome, but since one of the most compact and convenient forms of mechanism into which mechanical force can be stored is that of the coiled spring, and since the very nature of the spring is such that its force decreases as it uncoils, we must employ some compensating device between this variable driving force and the constant resistance. The fusee does this in a most accurate and complete manner. As the fusee to the right is to compensate for the loss of force of the spring as it uncoils itself, the chain is on the small diameter of the fusee when the watch is wound up, as the spring has then the greatest force.

"In the differential, or Chinese windlass (Fig. 23), different parts of the cylinder have different diameters, the rope winding upon the larger and unwinding from the smaller. By one revolution the load is lifted a distance equal to the difference between the circumference of the two parts.

"Before closing I may add a few problems for you to solve at your leisure by the application of the rules I have given you when describing the other mechanical powers.

"The pilot wheel of a boat is 3 feet in diameter; the axle is 6 inches; the resistance of the rudder is 240 pounds. What power applied to the wheel will move the rudder? Here the difference between the axle and wheel is 18 inches.

"Four men are hoisting an anchor of 3,000 pounds' weight; the barrel of the capstan is 8 inches in diameter; the circle described by the handspikes is 7 feet 6 inches in diameter. How great a pressure must each of the men exert?

"With a capstan four men are raising a 1000-pound anchor; the barrel of the capstan is a foot in diameter; the handspikes used are 5 feet long; friction equals 10 per cent. of the weight. How much force must each man exert to raise the anchor?

"The circumference of a wheel is 8 feet; that of its axle is 16 inches; the weight, including friction, is 85 pounds. How great a power will be required to raise it?

"A power of 70 pounds on a wheel whose diameter is 10 feet balances 300 pounds on the axle. Give the diameter of the axle.

"An axle 10 inches in diameter fitted with a winch 18 inches long is used to draw water from a well. How great a power will it require to raise a cubic foot of water, which weighs 62¹⁄₂ pounds?"

The first mail in the morning brought word that the whole of the partly prepared stuff for the boat had been shipped by "fast freight," and that it would reach its destination in the course of a few days. The paper patterns, directions, and all necessary instructions for building would be mailed at once.

IV

MAKING A GASOLENE LAUNCH

Each rib was numbered, and marked or stamped "right" or "left," and all the pieces were cut off to the right length and to the right bevel or angle to suit the positions they were to occupy, as specified in the printed instructions. This made the setting up an easy matter, requiring only care, patience, and a fair knowledge of the use of wood-working tools. That Fred possessed these qualities, was partly due to the training he had received in the technical school, and partly to his natural aptitude for picking up methods, ideas, and new applications.

Fred, George, and Mr. Gregg himself, were much interested in the selection of the various materials, and when the plank that was to form the keel had been unpacked, George was anxious that it should be laid down on the bed that had been prepared for its reception. He was quite disappointed when he found it considerably shorter than he had expected the boat to be. It was explained to him, however, that the overhanging of the stern, and therefore shortening of the forefoot, or stem, necessitated the keel being shorter than the boat would be when measured over all on top. The keel was found to be a fine piece of tough oak, nicely dressed, made the proper shape at each end, bored and gained to receive the stern post, the stern ribs, and side stanchions. Everything was marked, and each timber was sized so that it would fit in place snugly without using a tool on it, except a hammer or mallet.

At tea time George felt it difficult to keep reasonably quiet, he was so enthusiastic about the boat—much to the amusement of his father, who knew exactly how the boy felt.

After tea, all walked to the boat house, and the father assisted Fred to set up the keel, which was in two pieces, halved together midway and well fastened with screws. The joint was painted with a heavy coat of white lead and linseed oil paint, before being put together and screwed up. The keel is the lowest timber in a boat or ship, and it runs nearly the length of the craft. Sometimes there is a keelson placed on the top of the keel, and the ribs of the boat, or stanchions, are made fast to that timber, as shown in the illustration, (Fig. 24,) in which the gains for the ribs or moulds are made. This portion of the boat was put together temporarily, so Fred had no difficulty in assembling the various pieces. The stem, keel, keelson, and deadwood were all made of oak, and looked strong. The keel and keelson were properly laid and adjusted, and after some explanations by Mr. Gregg the manner of setting up the ribs was thoroughly understood. Fred decided to telephone Walter Scott to come down next day, as it was Saturday, and help him to set up the skeleton.

As the weather was getting warm, the whole family spent the evening on the veranda and George introduced the question of naming the boat. He suggested Red Bird, but this did not seem to take well, and several others were proposed but none seemed to suit everybody. Jessie sat quietly on the steps till asked by Fred what her choice would be.

"I would like it called after mamma, Caroline."

"That's a good idea, Jessie," said her father, "and if the boys or your mother don't object, I think we'll settle on Caroline."

Early next morning the boys were out watching for The Mocking-Bird, which very soon made its appearance. Fred and Walter tied the boat up to the new dock and went into the boat house, where the latter began to examine the boat stuff, and to explain the manner of setting it up and fastening it in place.

Nick, who was on hand to help, did the heavy work, and helped to put up the stanchions. Walter seemed quite familiar with the work, and he and Fred soon had the boat so well in hand that it seemed to grow under their fingers. The ribs were easily selected, as they were tied together in pairs and numbered. They were then set in their places according to their numbers and were fastened to the keelson with the strong copper nails. All the nails required for the boat were of copper, because that metal is less likely to corrode than iron or steel.

It was found necessary to brace the ribs in order to keep them in line. Thin pieces of lath were tacked on the tops to hold the ribs the proper distance apart, and longer and stronger strips of wood were used for bracing the boat sideways. These were nailed to the joints in the ceiling or high up on the walls of the boat house.

At noon the boys had the skeleton of the boat well advanced, and to one standing in front of the bow, it presented an appearance like the sketch shown at Fig. 25.

The launch might be called "carvel ribbon built," or nearly so, and it would have a displacement of 14 or 15 hundred-weight when fairly loaded. This weight would bring her down to the third W. L., as shown in the end sketch. To load her to the fourth W. L., would give her a load far beyond these figures. The sections had to be closely spaced, and the ribbons or slats let into the temporary section moulds before the outside boarding could be put on, the edges of the boarding being clinch fastened, as shown in the ribbon carvel, Fig. 26. Other styles of sheathing boats, as shown, are often used, but the Caroline was "ribbon carvel."

It is usual to lay off the sheer profile on a suitable floor, and line in the rebate line, scarf of stem, deadwoods, fork timbers, etc., making thin moulds of each member to be lined off, sawn, and bolted together. The section moulds, from which the boat derives its shape, are also laid off, and the planking, ³⁄₈-in. thick, deducted when making them.

The stem, of crooked oak, was 2¹⁄₄ in. thick by about 3 in., shaped as shown in Fig. 24. The fore deadwood was 2¹⁄₂ in. thick, moulded about 3 in., and through-bolted to the stem and keel with ³⁄₈-in. copper bolts; and the stern-post, 3¹⁄₂ in. thick, was wrought to shape, as shown. The centre line of the shaft, as shown, is subject to alteration, since different makes of motors have different sizes of propellers and flywheels. The fork timbers were let into the stern-post, and carried the transom, wrought out of a flitch of elm 3¹⁄₂ in. thick. The planking, of ³⁄₈-in. cedar, was closely jointed and varnished, and secured to the ribbons. The timbers were of rock elm, ⁷⁄₈ in. by ¹⁄₂ in., steamed and bent or sawn to shape, and through-fastened at the top and bottom edges of the planking. These were spaced on 7¹⁄₂-in. centres, with two clinch nails into the ribbons between them. Three or four solid floorings should be worked into the motor space; fitting of the motor bed thwartships gives great support to the boat.

The thwarts were of oak, 8 in. wide and 1 in. thick, with the side seats, ⁷⁄₈ in. thick, supported by turned legs of oak. The decks at each end should be of ¹⁄₂-in. oak or cherry reeded into 3 in. widths, and filled with marine glue. The covering board, 2¹⁄₂ in. wide, with a nosing worked on the edges, and ¹⁄₂ in. thick, was carried by a clamp or binding stake, 2¹⁄₂ in. by ⁵⁄₈ in., through-fastened at every timber. The knees were of oak, 1 in. thick, about 10 in. on the foot by about 3 in. at the head, and through-fastened. A breast hook 2 in. thick should be fitted. The floor boards may be of ³⁄₄-in. spruce, elm, or ash grating, as preferred. The centre of the motor was at No. 6 section, as indicated, the gasolene being stored in a strong tank under the forward deck, just high enough to feed by gravitation. After being cleaned off and sandpapered, a coat of good shellac varnish, may be followed, if desired, by three coats of best yacht varnish. The spacing of the sections was: No. 1, from face to stem, 1 foot 2 in.; No. 2, from No. 1, is 1 ft. 2 in., the other sections to No. 11 each 1 ft. 6 in.; No. 12 was 1 ft. 1 in. from No. 11 (see Fig. 25). The water-lines were 5 in. apart, and the buttock-lines, A and B, 1 ft. and 1 ft. 9 in. respectively from the middle line.

The boys followed these directions, and with the help of the following table, managed to get the boat ready to varnish and finish up. The following table, which refers more particularly to the section shown in Fig. 25, shows the sheer lines, counting from L W L (low water line). While all the work and calculations regarding the plan had been already done, Mr. Gregg, who had watched the work's progress for a week, thought they should know the principles on which the craft was being built, and therefore advised them to examine the illustration and table, so that they would have some knowledge of the science required to build a boat intelligently. Fred and George did this, and were helped along by Walter, who seemed to have mastered the subject pretty thoroughly.

TABLE OF OFFSETS

TABLE OF OFFSETS. Continued

TABLE OF OFFSETS. Continued

It was necessary, before installing the motor, that a foundation should be laid for it, so varnishing and the final finish were left over until the engine and propeller should be put in and tried.

The engine was brought to the boat house from Newark, and the expert, engaged by Mr. Gregg some time previous, came along with it, bringing such tools as he might want. He examined the bed for the engine, and saw that all was properly fastened and in good condition to place the engine and the propeller shaft. Mr. Watts (the machinist) laid off a line for the propeller shaft and with a long auger bored a hole from the engine bed through to the stern-post, large enough to permit the shaft of the propeller to revolve in it easily. A bearing, or "box," was adjusted to the stern-post in which the shaft ran, and the "box" was made water-tight to prevent any inflow. The propeller was made of bronze, had been nicely fitted to the shaft before it came, and had a set screw in its hub to hold it firmly on the shaft. The diameter of the propeller wheel measured 15 inches and it had two blades. The shaft and wheel being properly adjusted, the next thing was to place the engine, which weighed about 200 lbs. The blocks and tackle used in taking down the old barn were rigged up to the ceiling by cutting a hole through the floor, laying a short timber across the joists, hitching a rope around the timber, and letting a loop hang down through the hole made in the floor. The hook of the upper block was attached to the loop, a sling was fastened to the engine, the whole was hoisted by Nick with the greatest ease, and the machine dropped on its bed. As it did not lie quite level, it was raised again and held suspended until the bed was trued up, when it was permanently lowered into place and fastened down. Two views of the engine are shown in Figs. 27 and 28.

In "shop talk," the engine may be described as follows—Bore of cylinder 4¹⁄₂ in. Stroke 4¹⁄₂ in. Crank shaft 1³⁄₈ in. Revolutions per minute from 60 to 750. Propeller shaft one inch. About 15 or 16 horse-power. A float-feed carburetor, Fig. 29, was installed at the same time. This carburetor is an excellent one. It insures a regular supply of gasolene and air, in proper proportion, and prevents trouble when the motor is in use. The float guarantees an even level of gasolene in the float chamber at all times. The proper balance of the cork float closes the supply of gasolene automatically when it reaches the proper level. This prevents waste of fuel, every drop being thoroughly vaporized and mixed with the proper amount of air. The spraying nozzle is higher than the gasolene in the float chamber, and prevents the gasolene from getting into the engine, unless it is running. The throttle valve on the carburetor gives the operator the power to change instantly the speed, without changing the timer, and affords him absolute control of the engine.

When all the machinery was in place, and the propeller attached, Mr. Watts told the boys that he would finish up the work of installing the next day, and would then run the engine "dry" for an hour or two, to get everything working nicely before declaring the Caroline ready for sea.

It was just two weeks from the day the stuff arrived when the engine was finally installed.

"That's pretty quick work," declared Walter, "and if the boat were varnished, we could have her in the water in a couple of days."

In the evening, as all the Greggs were seated on the veranda, Fred tried to explain to his father the installation of the engine, but he failed to make himself quite clear.

Mr. Gregg said to him: "You seem to have grasped the theory of the matter, but I see you don't understand some important points, so I think a few suggestions may be of use to you. I will not confine myself to marine motors altogether, as gasolene engines are used for many purposes, more and more every day. With regard to installing an engine in a boat, the first question is the bed, as you have seen in your own case, where your foundation is made good and solid.

"Small engines may be supported upon a single cross piece at each end of the bed, but this method should be employed only for the smallest sizes.

"The heaviest, and in most cases the hardest, pipe to fit up is the exhaust. It runs from the exhaust nozzle on the engine to the muffler and thence outboard.

"The muffler is commonly placed in the stern with the outlet directly outboard. It may, however, be in any convenient position, like under the seats in the standing room, and the piping led outboard. In any case, the piping for the exhaust should be as direct and as free from sharp bends as possible.

"When the motor is near the middle of the boat, a good practice is to lead the exhaust pipe out through the bottom, and along it to a point near the stern, where it again enters the boat and connects with the muffler. The outlet from the muffler then leads directly outboard as before. This method, especially on a large cabin boat, avoids much loss of space and the disagreeable heat of the exhaust pipe. The surrounding water quickly cools the exhaust, reduces the pressure and makes the exhaust almost noiseless.

"The particular function of the muffler is to afford a comparatively large space into which the exhaust may pass and expand, greatly reducing the pressure. The gas, under the reduced pressure, then passes out with little disturbance. The muffler need be of no particular shape, as long as the volume is sufficient. It is usually made of cast iron in the smaller sizes and of sheet iron in the larger. In many cases a long piece of rather large pipe will answer the same purpose.

"The muffler may be dispensed with and much space saved by carrying the exhaust directly through the bottom of the boat and exhausting under water. Although this is a very convenient and many times satisfactory way, great care must be used or poor results will be obtained. When the exhaust leads directly out, a certain amount of pressure is used in displacing the water. This pressure is, of course, supplied by the piston and is a 'back pressure,' retarding the piston and decreasing its power.

"A small expansion chamber or muffler should be provided between the engine and the outlet, in order to break up the violent pulsations and make the flow fairly constant. Some form of shield should be fitted over the outer end of the exhaust pipe to guide the stream of the exhaust aft and prevent the water being forced into it by the movement of the boat. Several forms of these are on the market in the shape of brass castings which bolt on to the outside of the hull and have a thread on the inside to take the exhaust pipe.

"When the under water exhaust is fitted, a pet cock should be put in the exhaust pipe near the engine. This is opened when the engine is stopped, thus preventing the water from being drawn up into the cylinders by the vacuum caused by the cooling of the gases in the pipe and cylinders.

"The under water exhaust is a very neat and simple method, when correctly installed, as all noise and heat from the exhaust pipe are avoided. The exhaust may be considerably cooled and the noise reduced by dispersion.

"With regard to stationary engines, used for domestic or other purposes, any old place is considered good enough to put them in. Now, this is one of the biggest and most expensive mistakes one can make, for as soon as some small screw gets loose in the far corner, the engine, salesman and manufacturer are unjustly blamed, simply because the present owner has not left enough room to make the small adjustments necessary in every engine and piece of machinery. Therefore, it pays always to install the engine in a light, dry place, easy of access and with sufficient space all round to enable all parts to be reached and to give plenty of room for turning the fly wheels in starting. Whenever possible, place the engine on the ground floor. On an upper floor, the necessary provision should be made to avoid vibration; if installed in the basement, place it in the best light.

"Without a good foundation, an engine may be expected to give more or less trouble from vibration, since it is subjected to forces, suddenly and repeatedly exerted, which produce violent reactions. Care should be taken to excavate down to good soil and to line the bottom with a substantial thickness of concrete in order to form a single mass of artificial stone. The foundations may then be built up of either concrete, brick, or stone. Anchor plates should be extended to the bottom of the masonry and fastened so as to prevent turning while the nuts are being screwed up. Place gas pipes or tubes with an inside diameter twice the diameter of the bolts around them, while the foundation is being built; this allows the bolts to be adjusted, and any variations between the tubes may be filled with thin cement after the engine is set.

"The top of the foundation should be finished perfectly flat and level with a dressing of cement, and after this is thoroughly dry the engine may be placed in position. When bolting down the engine, it is better to draw each bolt down a little at a time until all are tight and thus avoid straining the engine crank. After the nuts are drawn tight, if the crank turns unreasonably hard without loosening the main bearing caps, it may indicate an uneven foundation, which is a strain in the engine bed casting.

"When setting up large engines, for farm or other purposes, especial care must be taken to avoid straining the bed castings. Foundations hung from an upper floor, or built upon it, should be placed as close to the wall as possible. For the smaller sizes of engines it is a good plan to lay wooden beams on top of the foundations and then to place the engine on top of them so that when the frame is bolted down it beds itself into the timber. The timber cap often saves an annoying vibration when it can be overcome in no other way.

"All the connections should be as short and as free from turns as possible, and no mistake can be made by having plenty of unions, so as to disconnect with ease. The gasolene tank should be set as near the engine as is convenient, with the top of the tank, preferably, not more than a foot or two below the base of the engine. In cases where the gasolene tank must be set from forty to fifty feet away, it is necessary to place a check valve in the suction pipe near the tank. Both suction and overflow pipes must have a gradual rise all the way from the tank to the pump and should be as straight as possible to avoid the air traps, which prevent a steady flow of gasolene. It is most essential to clean thoroughly all pipes and fittings before they are put together, by hammering lightly to loosen any scale and washing out with gasolene, as solid matter of this nature may be responsible for some of the simple, but hard-to-get-at troubles common to gasolene engines.

"Shellac is best for joints in gasolene piping, but when this cannot be obtained common laundry soap will answer the purpose just about as well. Remember, also, that gasolene is a rubber solvent, and should never be applied to joints where rubber is used. In some cases it will be found advisable to use gravity feed instead of a pump, except in the case of the tank, which must be so arranged that its lowest point is slightly above the generator valve.

"The exhaust pipe must be of full size, free from turns and short as possible, since the shorter it is the more economically the engine will run. It will be found advisable to place the muffler and exhaust piping away from combustible material, and never to turn the exhaust into any chimney or flue.

"There are two general methods of supplying the water, the first being that of the cooling tank commonly used with small engines. For convenience in piping, the tank should be slightly elevated, and both pipes, having as few bends as possible, should slope from the tank to the engine, a valve being placed in the bottom pipe near the tank. By using a circulating pump, fitted to the engine or shaft, water may be used from an underground cistern or tank.

"The other method is to use a continuous cooling stream from water-works or other source. When city water is used, it is a good plan to have a break and funnel inserted in the drain pipe so that the current of water flowing through the cylinder jacket may be seen. For making joints in water pipes, either thick lead or graphite may be used with almost equal success. It may be well to place particular emphasis on the fact that it will pay to get into the habit of always shutting off the water at the tank and draining the cylinder every time the engine is stopped—not necessary in summer, but absolutely essential in winter—as a fair percentage of gasolene users know to their cost.

"The greatest care must be employed in using and handling gasolene, as it is dangerous and highly explosive. It has been known to explode when 20 or 30 feet from light, the vapours having reached the fire in the way of a gas, igniting and firing the liquid. And, now, right here, let me impress on you this warning; never handle gasolene near a fire or light under any circumstances, and be very careful with it under all conditions.

"Fortunately, there are few accidents resulting from gasolene, when we consider the large amount used since it has become almost a universal fuel for engines, and it is also used largely for domestic heating and lighting.

"It is a product of petroleum, of which in its crude form about 76 per cent. is turned into kerosene, 11 per cent. into gasolene, 3 per cent. into lubricating oils, and the balance into vaselines, paraffine, coke and so forth.

"Different petroleums produce different proportions of the various products, some of them being considerably richer in gasolene than 11 per cent.

"Gasolene is usually designated according to its specific gravity by an arbitrary measure, known as Baume's hydrometer scale. This designation is in degrees, the most common gasolene ranging between 65 degrees and 85 degrees, and the average being 70 degrees, the usual density used in engines.

"You will find it somewhat difficult at first to start up your engine when you wish to, so I will give you a few hints to show how this difficulty may often be overcome.

"There is always a reason why a gas engine refuses to obey the behest of its driver.

"In the first place, see that the compression is right and the admission valve so tight that it will admit only enough of the mixture (gasolene and air) to make a charge that will take fire from the sparker and move the piston forward. Next see that the sparker is clean, that it will make a bright spark at white heat when the contact is broken, and at the right time. 'In time' means to go if everything else is right, and 'out of time' means not to go even when everything else is right.

"The valve of the engine must be kept well ground down with emery and oil so as to preclude the possibility of a leak, as one would very seriously weaken the power of the engine even after it had started. The spark must be made when the connecting rod of the engine is on the 'up stroke,' with the crank shaft about three inches below the horizontal line of the centre of the index, and herein lies the whole secret of the greatest efficiency from the least amount of gasolene. As there is an interval of time after the spark is made until it ignites the charge, it is very evident that the movement of the machinery continues and the moment of ignition should take place when the compression is greatest. This will be when the piston is on its farthest 'in stroke,' i. e., in perfect line with the centre of the cylinder. But if the charge be ignited at this point the engine will not develop the greatest power, as the interval spoken of will elapse and the piston will have started on its 'out stroke', thereby not getting its full force of the expansive gases liberated by combustion of the air and gasolene.

"So you will readily see that you must allow for the interval spoken of, if you would get full returns for the energy used in propelling the motor. I have tried to make this plain, and I hope my efforts will help you out with your engine, either in starting or developing the power at which it is rated."

It was not yet late, so the boys took down from the book shelf a code of yacht flag signals, and found the following:

"There are no hard and fast rules regarding shapes and colours of yacht bunting, but the following are generally accepted by the prominent clubs in the United States and in foreign countries.

1. The "pennant" (a triangular shaped flag) is used for the club burgee.

2. The "shallow tail" is adopted for the private signal.

3. The rectangular flag is chiefly used for a flag officer's signal.

4. The shape, consequently, at once denotes whether a flag is that of a club, a flag officer, or a member.

5. The majority of flag officers' signals are coloured: Blue for commodore, red for vice-commodore, and white for rear-commodore.

6. The international code of signals enables yachts to communicate with each other, and is also used for dressing ship.

The ensign should be flown from the peak of the main-sail on a sailing yacht, when under way, and from a stern flag pole when moored.

On a yawl, it should be hoisted at the mizzen truck.

On a steamer, launch, or dinghy, it should be flown from a stern flag pole, when under way or at anchor.

Club Burgee.—The burgee should measure in length about one-half inch for each foot of height of truck from the water; width to be two-thirds of the length. Private signals may be smaller.

The burgee should be flown from the mast-head or truck of a cutter, sloop, or cat-rigged yacht, the main truck of a yawl, the fore truck of a schooner and steamer, and from the bow pole of a launch or dinghy.

Flag officers' and private signals should be flown from the truck of a cutter, sloop, or cat-rigged yacht, the main truck of a schooner, yawl, or steamer, and from the bow pole of a launch or dinghy.

The following flags are not considered as colours:

Night Pennant (blue).—Is hoisted at the main truck from sundown to 8 A. M.; also occasionally used as a tell-tale when racing or sailing.

Owner's Absent Flag (blue rectangular).—Is flown from the main starboard spreader when yacht is at anchor only. It denotes owner is not on board, but should never be flown when under way.

Owner's Meal Flag (white rectangular).—Is flown from the main starboard spreader, and denotes the owner is at meals—boarding a yacht when this flag is flying is considered bad form.

Crew Meal Flag (red triangular).—Is flown from the foreport spreader on schooners and main-port spreader on single-masted yachts. This denotes that the crew is at meals.

The Ensign.—Displayed on a vessel indicates distress and want of assistance.

Flag "B," of the International Code of Signals, is used for a protest flag, and is conspicuously displayed in the rigging of a yacht protesting during a race.

A yacht, on withdrawing from any race, should at once lower its racing colours, and allow yachts still competing the right of way.

This code was studied by the boys until both of them thoroughly understood its full meaning, and George became so enthusiastic over it that he exclaimed: "Fred, I am going to be an admiral of the navy!"

V

A TALK ABOUT ENGINES

George seemed to grasp the idea thoroughly. Mr. Watts also explained the use of the carburetor, the spark coil, the battery, and the method of contact to produce a spark at the proper moment. After some screwing of bolts, adjusting the piston, and trying the valves, the tank in the carburetor was supplied with gasolene and Mr. Watts tried the engine for a few revolutions, as gently as it could be done. It was a little stiff at first, some of the connections fitting too tight, and the piston, being new and harsh, did not work smoothly. By the judicious use of good lubricating oil and a few turns of some of the nuts on the bolts, a little more freedom was given to the machine and the starting was easy and smooth. George and Jessie were delighted with the rapid movement of the machine, the buzz of the propeller, and particularly interested in the movement of the water in the tub.

Mr. Watts allowed the engine to run quite a little while, and arranged the exhaust so as to beat regularly and to "pop! pop!" as little as possible. He then called Fred into the boat and taught him how to run the machine, arrange the contact breaker, and regulate the feeding of fuel. The engine was stopped to cool and to be examined again by Mr. Watts, who pronounced it all right. Mr. Gregg, who had arrived just before the engine was stopped, examined all its parts and watched it work for a minute or so.

Fred arranged his pots and brushes, and he and George went to work varnishing, so that before sunset the Caroline looked quite smart and trim. The boys were very careful in applying the varnish to put it on light and thin so as not to let the coats lap over one another as they went along. They finished each "streak" from end to end, before starting on the next, and following this method they obtained a nice, even surface. The varnish did not look "blotchy" or patched, as it would have done had the ends of the varnish lapped. To avoid "lapping" is one of the most essential operations in varnishing, when a nice piece of work is desired.