[False destroying Decks.] William Bourne, in his “Inventions of Devices,” 1578, devotes the “Third device” to show—“How to use a plain or open deck hatches, that it is not possible to enter the ship without spoiling of the enemies.”

14.

How to bring a force to weigh up an Anchor, or to do any forcible exploit in the narrowest or[8] lowest room in any Ship, where few hands shall do the work of many; and many hands applicable to the same force, some standing, others sitting, and[9] by virtue of their several helps a great force augmented in little room, as effectual as if there were sufficient space to go about with an Axle-tree, and work far from the Centre.

[Multiplied strength in little room.] We shall have to allude to the ambiguous use of the word “force” in the same sentence, as indicating “strength, power, &c.” or, “a pump, or pump plunger,” in John Bate’s, and other old works on mechanics. Now if we were to read this, “How to bring the force [or plunger of a pump] to weigh up an anchor, &c., and many hands applicable to the same force [or pump], &c.”—we should have a statement strongly indicating the modern contrivance of the hydraulic press. The concluding portion of the sentence only serves to strengthen this suggestion. See “force” used in No. 21.

In 1594, Edmund Jentill, writing to Lord Burghley, mentions, as his fourth invention:—“A devise whereby two men may be sufficient to weigh the weightiest anchor in her Majesty’s navy, with greater expedition than it is now done with the number now used.” Also, “The like device is found for the hoisting of the main-yard with the like expedition.”—MS. Lansdown, 113, Art. 4: and, “Letters on Scientific Subjects,” edited by J. O. Halliwell, F.R.S. 8vo. 1841.

15.

A way[1] how to make a Boat work it self against Wind and Tide, yea both without the help of man or beast; yet[2] so that the Wind or Tide, though directly opposite, shall force the Ship or Boat against it self; and in no point of the Compass, but it shall be as effectual, as if the wind were in the Pupp,[3] or the stream actually with the course it is to steer, according to which the Oars shall row, and necessary motions work and move towards the desired Port or point of the Compass.

[A Boat driving against wind and tide.] The wording of this article is varied as follows in the MS. of certain of his Inventions. See Appendix A. He therein states:—

“By this (his quintessence of motion), I can make a vessel, of as great burden as the river can bear, to go against the stream; which, the more rapid it is, the faster it shall advance. And the moveable part that works it, may be, by one man, still guided, to take the best advantage of the stream; and yet to steer the boat to any point. And this engine is applicable to any vessel or boat, whatsoever, without being, therefore, made on purpose; and work these effects:—It roweth; it draweth; it driveth, if need be, to pass London bridge against the stream, at low water. And a boat lying at anchor, the engine may be used for loading or unloading.”

He made this invention one of the four subjects in his Patent of 1661 (see Appendix B), which again varies the reading; but this last plainly indicates the motive power as having been a mill. He proposes in his patent specification:—“To make a boat that roweth, draweth, or setteth even against wind or stream, yea, both, and to any part of the compass which way soever the stream runs or wind blows, and yet the force of the wind or stream causeth its motion, nothing being required but a steersman; and whilest the boat stayeth to be loaded or unloaded, the stream or wind shall perform such work as any water-mill or wind-mill is capable of.”

Among the Harleian MSS. in the British Museum, there is an Italian book of sketches on parchment, No. 3281, attributed to the 15th century, entitled, “Delineationes Machinarum;” from one of the pen and ink drawings of which the annexed engraving is a reduced copy. It is a paddle boat of a very primitive form, to be operated by men working at two crank handles. The Marquis seems to have had a very similar idea, only employing the mechanical arrangements of a suitable wind or water-mill.

In that fine work, “Vitruvia de Architectura,” folio, Como, 1521, there is an engraving of a large vessel propelled by paddles, worked by animal power; therefore, so far as such a mode of propulsion is concerned, paddle-wheels are of very ancient origin. In 1574, Ralph Rabbards[J] presented to Queen Elizabeth, through the medium of the venerable Lord Burghley, a list of twenty-five inventions. The 24th is:—“The rarest engine that was ever invented for sea service. A vessel in manner of a galley or galliotte to pass upon the seas and rivers without oars or sail, against wind and tide, swifter than any that ever hath been seen; of wonderful effect both for intelligence, and many other admirable exploits, almost beyond the expectation of man.”

William Bourne, in his “Inventions or Devices,” published in 1578, most of which he claims to be his own projects, yet acknowledging some to have been borrowed, offers the following in the 19th Device without comment:—“And furthermore you may make a boat to go without oars or sayle, by the placing of certain wheels on the outside of the boat, in that sort, that the arms of the wheels may go into the water, and so turning the wheels by some provision, and so the wheels shall make the boat to go.”

This is followed by another application, being the 20th Device:—“And also, they make a water-mill in a boat, for when that it rideth at an anchor, the tide or stream will turn the wheels with great force, and these mills are used in France, &c.”

In 1583, proposals were made for 20 different inventions, but the author’s name does not appear. The 19th is:—“To make a boat to go fast on the water without oar or saile;” but this is all we learn of his project. See “Rara Mathematica,” edited by J. O. Halliwell, F.R.S. &c. 8vo. 1841.

In 1594, Edmund Jentill addressed to Lord Burghley two communications respecting his inventions. The last he names thus:—“A device wonderful strange is also found out, whereby a vessel of burden may easily and safely be guided both against wind and tide.” MS. Lansdown, 113, Art. 4; and “Letters on Scientific Subjects,” edited by J. O. Halliwell, F.R.S. &c. 8vo. 1841.

Cressy Dymock, in his letter published by Hartlib in the “Legacie; or an enlargement of the Discourse of Husbandry,” 4to. 1651, describing what he saw at Wicklesen, mentions—“a pretty kind of Pinnace with ordinance, somewhat like a close litter, but flat-bottomed; which rowed with wheeles instead of oares, imployed it seemes formerly with admirable successe, for the taking in of Crowland, and which gave me a proofe of what I for many years have thought possible, and of very great use and service, and still think it of unknowne value, if it were skilfully indeed framed, and applyed as it might be.” [p. 110.]

Samuel Cotton, on the 28th of January, 1619, obtained a patent for making and erecting mills upon barges or lighters in the river Thames.

David Ramsey and Thomas Wildgoose, on the 17th of January, 1618, patented, among various other inventions, one “to make boats for the carriage of burthens and passengers run upon the water as swift in calms and more safe in storms than boats full sailed in great winds.”

David Ramsey includes in his patent of 21st of January, 1630, his invention “to make boats, ships, and barges to go against the wind and tide.”

And Dr. Thomas Grent, on the 20th of July, 1632, patented a plan “for a more speedy passage of calmed ships.”

In 1640, Edward Ford, patented his invention, whereby he can make all boats, &c. “go faster against wind and tide than now they use to do, with half the men they have formerly used.”

It is stated in “Frier Bacon’s discovery of the Miracles of Art, &c.” published in 12mo. 1659, that—“It is possible to make engines to sail withal, as that either fresh or salt water vessels may be guided by the help of one man, and made sail with a greater swiftness, than others will which are full of men to help them.” Chap. iv. p. 17.

In “Humane Industry,” 1661, chap. 10, p. 154, it is noticed—“The ancients had a way to drive their ships without oar or sail, so that they could never be wind bound.” And at page 155, it is observed that—“Scaliger doth aver, that he could make a ship that could steer herself.”

Thomas Togood and James Heyes, in 1662, patented their invention for the making of ships to sail without the assistance of wind or tide.

16.

How to make a Sea-castle or Fortification Cannon-proof, and[4] capable of a thousand men, yet sailable at pleasure to defend a passage, or in an hours time to divide it self into three Ships as fit and trimm’d to sail as before: And even whilest it is a Fort or Castle they shall be unanimously steered, and effectually be driven by an indifferent strong wind.

[A Sea-sailing Fort.] Vitruvius, Vegetius, and many ancient writers supply a variety of schemes to direct an inventor’s ingenuity. The idea of such a construction, to divide into three or more sailing vessels is likewise suggested, in many early designs, although no doubt very different in some details. But the peculiarity hitherto unnoticed, of the present invention, consists in the propelling and steering by means of an artificial current of air. It is very clear that the Marquis had discovered some pneumatic mode of propulsion. There is no inconsistency in the idea of the same means being adapted for both steering and propelling alternately. Even within the last few years extensive experiments have been made, in which air-pumps were used to compress the air beneath an inclined plane under the stern, which in flowing upwards gave motion to the vessel.

17.

How to make upon the Thames a floting Garden of pleasure, with Trees, Flowers, Banquetting-Houses, and Fountains, Stews for all kind of fishes, a reserve for Snow to keep Wine in, delicate Bathing-places, and the like; with musick made with[5] Mills: and all in the middest of the stream, where it is most rapid.

[A pleasant floating Garden.] There appears to be little more invention here than in the contrivance of so much variety, and the selecting of “the stream where it is most rapid,” to give motion to the water-mills to work the bellows for producing the promised music; as well as to raise water high enough to obtain a pressure of it for making the snow. The whole offers one of those raree-show designs in which our great-grandfathers delighted, and the descriptions of which formed the staple of their scientific discussions in polite society.

18.

An Artificial Fountain, to be turned like an Hour-glass by a child, in the twinkling of an eye, it[6] holding great quantity[7] of water, and of force sufficient to make snow, ice and thunder, with a[8] chirping and singing of birds, and shewing of several shapes and effects usual to Fountains of pleasure.

[An Hour-glasse Fountain.] In a MS. among the Marquis’s papers, the foregoing appears to be the invention indicated under the title:—“Fountains of pleasure, with artificial snow or hail, or thunder, and quantity not limited.” [See p. 316.]

Kircher, Schottus, and others give descriptions, with engravings of fountains, having the external appearance of the hour-glass. The process of turning may have been facilitated by the machine resting on two central pivots. But it must have been of considerable size to produce an efficient hydraulic pressure engine to give forth snow and ice. The thunder, &c., would depend on plans well understood for producing stage effects, and their introduction here, with the music of birds, &c. [see Article 46.] is similar to other automatic arrangements which were the wonder and delight of that age, and a much later period.

In 1755, an engine of peculiar construction, to raise water from an Hungarian mine, was erected by M. Hoel, at Chemnitz, which generated intense cold as the water and air rushed out together, under great columnar pressure, causing the formation of artificial hail, projected with amazing force; the effect being very analogous to the suggestions offered by the present articles, Nos. 17 and 18.

19.

A little engine within a Coach, whereby a child may stop it, and secure all persons within it, and the Coachman himself, though the horses be never so unruly[9] in a full career; a child being sufficiently capable to loosen[1] them in what posture soever they should have put themselves, turning never so short; for a child can do it in the twinkling of an eye.

[A Coach-saving Engine.] We have two other readings of this article; the first is the 5th article in his list of a portion of his Inventions, (see Appendix A.) as follows:—“By this (his quintessence of motion) I can make a child, in a coach, to stop the horses (running away), and shall be able to secure himself, and those that be in the coach; having a little engine placed therein, which shall not be perceived, in what posture soever the horses draw. A child’s force shall be able to disengage them, from overturning the coach, or prejudicing anybody in it.”

The second reading is in his patent of 1661, (see Appendix B.) wherein he offers:—“To make an engine applicable to any coach, by which a child of six years old may secure from danger all in the coach, and even the coachman himself, though the horses become never so unruly, the child being able in the twinkling of an eye to loosen them from the coach, in what posture soever they draw or turn, be it ever so short, or to either hand.” By means of a T-ended lever, two or four bolts could be simultaneously drawn inwards, and the horses thereby released with the greatest possible ease and certainty.

20.

How to bring up water Balance-wise, so that as little weight or force as will turn a Balance will be onely needful, more then the weight of the water within the Buckets, which counterpoised[2] empty themselves one into the other, the uppermost yielding its water (how great a quantity soever it holds) at the self[3]- same time the lower-most taketh it in, though it be an hundred fathom high.

[A Balance Water-work.] It is to be regretted that we have nothing at present to aid us in offering a description at all approaching the singular construction of this hydraulic machine. There are some curious designs given in the description of M. Grollier de Servière’s cabinet, 1719, but we have never seen any plan fully realizing the effect above indicated.

21.

How to raise water constantly with two Buckets onely day and night, without any other force then its own motion, using not so much as any force, wheel, or sucker, nor more pullies then one, on which the cord or chain rolleth with a Bucket fastened at each end. This, I confess,[4] I have seen and learned[5] of the great Mathematician Claudius[6] [7] his studies at Rome, he having made a Present thereof unto a Cardinal; and I desire not to own any other mens[8] inventions, but if I set down any, to nominate likewise the inventor.

[A Bucket-fountain.] In the present and preceding articles the water is elevated by means of buckets, and it was only while these pages were passing through the press that the author perceived those precise marks of distinction between the two methods of employing the buckets which enables him now to offer the following explanation of each.

As regards No. 20, it seems, at first, absurd to expect to raise water which is to be in a balance and pass from one bucket to the other. But let us suppose an arrangement, as in the subjoined engraving, where A, B, is a strong vertical wooden frame carrying six metal or wooden pipes C, C, which can be moved simultaneously up and down on centres, a, a, being connected by the iron rods, b, b; these pipes are united with the top of six buckets at D, D', and with the bottom of six other buckets at E, E'. The buckets D, D', are also connected at the bottom with six other pipes F, F, each open at the end F, F, and so arranged that the topmost pipe passes over a pulley c, but the other five pipes with guide rods d, d, at their ends, enter the top end of the five uppermost buckets on the side E; the pipe F, passing over c, delivers the contents of bucket D, while the lower-most bucket E', is being replenished, “thus the uppermost yielding its water at the same time when the lower-most taketh it in.” In the present position of the machine the pipes C, C, are inclined, and the pipes F, F, are horizontal, but when the bucket E' is elevated, then these pipes will all reverse their positions, being connected with the buckets by means of flexible leather hose, or suitable jointed metal tubing.

We have next to consider the present article No. 21. The conditions stated require the use of but one pulley, one cord, and two buckets, without any “force” or pump plunger, or “any wheel, or sucker.” An arrangement so simple seems only possible to be attained by some such plan as that exhibited in the illustration given below. We have here an endless chain or cord, A B, passing over the pulley C, with a bucket D, at the upper end; and another bucket E, at the lower end; the first in the act of discharging its contents into the trough G, the second re-charging with water at the level E. This endless chain is further supplied with a series of conical or other shaped buckets, a, a', set on the endless cord in a reverse direction, so as to receive water conveyed from an upper stream by the spout F, by which means the side B, of the cord will descend, and the side A, ascend, “without any other force than its own motion,” and that “with two buckets only, day and night.” On the side a', the conical buckets reverse and empty themselves, thereby lightening the ascending side A, of the endless chain or cord.

22.

To make a River in a Garden to ebbe and flow constantly, though twenty foot over, with a childs force, in some private room or place out of sight, and a competent distance from it.

[An ebbing and flowing River.] In reference to this invention Mr. Partington has quoted Peter Bogaerts’ ingenious method of a canal lock, so contrived that, in a model, a weight of seven pounds was made to raise ten hundred weight of water more than four feet in a few seconds.

But still the process of ebbing and flowing is not made out; it does appear, however, that its operation requires the constant services of a boy or other attendant, probably to keep alternately opening and closing certain sluice arrangements, placed somewhere concealed from view; the whole affording a water-work to amuse and surprise, and forming a variety on the usual strange schemes attached to grottos, caves, &c. spouting water in every variety of form.

See further the comments on article No. 57, which very probably includes the principle here employed by the Marquis.

There is no communication in this article of facts requisite to direct an engineer or inventor in the adjustment of any special kind of machinery to obtain the desired ebbing and flowing river; which is a novelty, in this respect, peculiar to the Marquis of Worcester’s ingenuity. He was evidently not copying or improving any anterior system of water-work. The next article is but an application of this new system; and it is not until he has taken us through descriptive hints of thirty-three totally different designs or devices, that in No. 57, he offers “A constant water-flowing and ebbing motion.” We think the three may be taken together, that is, No. 57, refers to the principle and mechanism, of which Nos. 22 and 23, are mere simple applications.

Thus, referring to what we have stated under No. 57, the purpose named in the present article might be attained by means of two domed or bell-shaped vessels, placed like gasometers, but otherwise immoveable, partially immersed in a pond, or other artificial piece of water; which being arranged so that, by admitting a steam pipe into each, the contained air could be driven out thereby, condensation would naturally follow, or might be accelerated; and one vessel immediately filling with water, while the other was emptying, the surface of the pond or river would be kept in a continual state of agitation, and the water might be said to “ebb and flow constantly, though 20 feet over.”

No reason is assigned for proposing this modification of water work, no advantage is pointed out, the Marquis doubtless depending on its apparent impossibility for its exciting and stimulating inquiry. He knew how the promulgation of such a wonder would have affected his own mind, and never imagined but that the public would feel equally inquisitive. His incomprehensible truths are, however, often denounced, without investigation, as though they were false.

23.

To set a Clock in[9] a Castle, the[1] water filling the Trenches about it;[2] it[3] shall shew by ebbing and flowing the Hours, Minutes and Seconds, and all the comprehensible motions of the Heavens, and Counterlibation[4] of the Earth, according to Copernicus.

[An ebbing and flowing Castle-clock.] John Bate, in his “Mysteries of Nature and Art,” 1635, at p. 45, describes—“A water-clock, or a glasse showing the hour of the day,” by three different arrangements.

This article is further noticed in commenting on No. 57.

24.

How to increase the strength of a Spring to such an height,[5] as to shoot Bumbasses and Bullets of an hundred pound weight a Steeple-height, and a quarter of a mile off and more, Stone-bow-wise, admirable for Fire-works and astonishing of besieged Cities, when without warning given by noise they find themselves so forcibly and dangerously surprised.

[A Strength-increasing Spring.] The technical term Bumbasses, or probably bombasses, here used, has escaped the attention of all compilers of Archaic Dictionaries. By the context we may presume it was applied to the large stones usually fired from bombards, and differing only from bullets in these last being made of lead or iron.

Ancient cannon appear to have consisted of two kinds; a large one for discharging stones, called a Bombard, and a lesser one for darts. In 1388, a stone bullet, weighing 195 pounds, is related, according to Meyrick, to have been discharged from a Bombard, called the Trevisan. Such stone missiles may have been of the kind called by the Marquis “bumbasses,” and would be perhaps more properly named bombasses. The Stone-bow was the Prodd; probably the Slurbowe was furnished with a barrel through a slit, in which the string slided, when the trigger was pulled. Three kinds are mentioned by Du Cange. See Fosbroke’s Encyclopædia of Antiquities, 8vo. 1840.

Bishop Wilkins, treating on Catapultæ in his Mathematicall Magick, 1648, observes that their usual form was “after the manner of great bows placed on carriages, and wound up by the strength of several persons;” adding: “These were sometimes framed for the discharging of two or three arrows together.”

As the Marquis wrote the Century in 1655, only seven years after Wilkins’ publication, it is not at all unlikely that he seriously contemplated the contriving of a most useful warlike implement; and this appears the more reasonable when we find the worthy and learned prelate advancing, as it appeared to him, cogent reasons in his 19th chapter, in favour of the “Military offensive engines used amongst the ancients,” as compared to cannon; gravely summing up his observations with the remark—“that the force of these Engines does rather exceed than come short of our gun-powder inventions.” Then again on the ground of expense he shows an advantage in favour of Ballistæ and Catapultæ. Thus: “the price of these gun-powder instruments is extremely expensive.” This is proved from “a whole Cannon weighing commonly 8,000 pounds, a half Cannon 5,000, a Culverin 4,500, a Demi-culverin 3,000,” which “must needs be very costly,” amounting “to several hundred pounds,” for which sum “at least 10 of the ancient timber made engines might be purchased”!

Then their transport was a serious matter, for “a whole Cannon does require at the least 90 men, or 16 horses,” and so in proportion for others. But the timber made engines are light, and their “materials to be found everywhere.”

Then the gun-powder is costly; “a whole Cannon requiring for every charge 40 pound of powder, and a bullet of 64 pounds,” and in proportion for lesser cannon; whereas those other engines may be charged only with stones. So that only for the superior force of cannon “those ancient inventions” he conceives to be “much more commodious than these later inventions.”

Among questions propounded and agreed upon, in January, 1660, to be sent to Teneriffe by the Lord Brouncker and Mr. Boyle, the fifth was,—“Try the power of a stone bow, or other spring, both above and below (the hill), and note well the difference.”—Weld’s Hist. Royal Society, Vol. i. p. 98.

25.

How to make a Weight that cannot take up an hundred pound, and yet shall take up two hundred pound, and[6] at the self-same distance from the Centre; and so proportionally to millions of pounds.

[A double-drawing Engine for weights.] The articles Nos. 25, 27, and 29 can only be taken as descriptive of elucidatory models, demonstrative of the applications of a certain principle, the result of condensation. For some unaccountable reason there has been a prevalent opinion that the Marquis was ignorant of condensation. If such an opinion is grounded on his not expressly alluding to it in the “Century,” then by the same rule it might be doubted whether he understood anything about steam! But as the “Century” was written to remind himself, and not to inform others of the modus operandi, it was sufficient for his purpose to particularise only the results. We can usually distinguish where he treads a beaten track, the result of reading, and where his course deviates into his “fire-water-work” experiments. The former generally has its parallel in some old author; but when the same rule is attempted to be applied to measure the others, we find we are dealing either with a new order of things, or else with sheer paradoxes of the most chimerical character. While, on the other hand, follow him in his own new track of experimental research, and we are rewarded at every step with a full and clear exposition of the wonderfully ingenious processes of inquiry by which he attained the perfection ascribed by him to his “Water-commanding Engine.”

In the present article it is required that a weight shall take up double its own weight, not by the old rule of leverage, but “at the self-same distance from the centre.” In the subjoined diagram we have two cylinders C, B, connected at the lower end with a steam pipe, supplied with the steam-cock A. A cord passing over the drum wheel D, is connected at its ends with the pistons B, C; and the whole stands in a trough E. Steam having been admitted to B, and then cut off, condensation has ensued, the piston B has descended and C has been raised, and along with it a quantity of water. Here we may take the two pistons as representing “one hundred pound” each, and although they balance, yet we thus find “how to make a weight” under such circumstances, nevertheless, take up “two hundred pounds,” that is, including the water.

A very similar kind of piston to the one here shown, is suggested by Fludd, Besson, and others, to be worked by a spiral spring, which being drawn to the bottom of a cylindrical vessel, water may be poured in above it, and being then tightly covered, with a lid having either an open jet or a tap in the centre, on releasing the spiral spring, the false bottom rising, and pressing the liquid, causes it to escape in a jet d’eau, gradually diminishing as the spring relaxes. The contrivance is elaborately illustrated in the 18th folio engraving of Besson’s “Theatrum Instrumentorum et Machinarum,” 1578; the Marquis, therefore, had only to substitute steam for the spiral spring.

26.

To raise weight as[7] well and as forcibly with the drawing back of the Lever, as with the thrusting it[8] forwards; and by that means to lose no time in motion or strength. This I saw in the Arcenal at Venice.[9]

[A to and fro Lever.] William Bourne offers the following as his 112th Device, “touching the making of engines to thrust from or pull to you with great force or strength.” He says, “And furthermore, you may make an engine to thrust from you or to pull unto you, to lift vp or to presse downe with great force, eyther to goe with wheeles as before is declared, or else to goe with skrewes or to goe with both, as to thrust open huge and strong gates, or else you taking good hold, to pull them open vnto you wards, and will make but little noyse in the doyng thereof, but you must be sure to set the engine fast, if to thrust from, to be strongly and well backed, and to pull to them it must be strongly bolstered before, sufficient to be of force to scrue the turne.”

The Venetian arrangement may be described, as shown in the annexed engraving, where A, B, C, is a frame, the two upright sides of which D E, are provided with a series of clicks, appearing in the drawing like the serrated edge of a saw, and each is so placed secured by a pin on which it moves, as always to incline to fall outwards. F, F, is a long lever, having a stout short cross bar in the centre, and is represented on the point of taking up on a click at a, while it leaves one on the opposite b, such being the to and fro motion required, thereby losing “no time in motion or strength.”

27.

A way to remove to and fro huge weights with a most inconsiderable strength from place to place. For example, Ten Tunne with ten pounds, and less; the said ten pounds not to fall lower then it makes the ten Tunne to advance or retreat upon a Level.

[A most easie level Draught.] The weight is in this case to be moved “with a most inconsiderable strength.” Ten pounds, or less, are to be capable of moving 22,400 pounds. And the precise conditions are—“the said ten pounds not to fall lower than it makes the ten ton to advance.” The annexed engraving shows, as in No. 25, two cylinders B, C, with their steam-pipe and valve at A, having above a platform G, on which is a loaded truck F, attached by a cord a, at one end passing over a pulley, and the drum wheel D, to the piston B; and a second cord at the other end passing over a pulley at a', attached in like manner to the other piston C. Steam having been admitted to B, on its condensation the piston descending draws along with it the weighted truck F, while the piston C, ascends, drawing in air at E.

We thus attain the strict letter of the conditions set down, the fall and the advance being equal.

28.

A Bridge portable in[1] a Cart with six horses, which in a few hours time may be placed over a River half a mile broad, whereon with much expedition may[2] be transported Horse, Foot and Cannon.