Gearing for parallel motion
To come to the point:—the smallfigure 4, inPlate 41, relates to this subject. My geering is there seen in three forms or applications—each one intended to bring the above property into play. The partn o, represents the manner in which two wheels with singly-inclined teeth, work together when one ofthem is furnished with a cheek, as directed infig. 3ofPlate 14. But here, in addition to that, the teeth of both wheels are slopedmoreon one side than on the other, so as to assumea wedge-like form: insomuch, that in beginning to work, (if notperfectlyformed) the wheels would not occupy the same plane. For, in fact, thecheek screwspress home the cheekoagainst a number of thin washers all round the wheel, and thus only draw the wedge-formed teeth into each other as they becomebedded, and successive washers are taken away. Hence, a good degree of precision is obtained—accompanied with little friction, and thus with great durability.
But we stop not here. The partp qof thisfigure, shews a pair of wheels doubly inclined—one of them only, being made in two halves, which are connected together by screws and washers, like that just described. Here then,anotherdegree of friction is got rid of—namely, that of the cheeko: but still, a small degree remains, (dependent on the double versed sine of the angle formed on the wheel’s circumference, by thethicknessof a tooth). This quantity, is indeed, very minute; and brings, perhaps, the whole near enough to perfection. To do, however, completely away with allfriction, (see my preceding statement)—as well in the wheel actingbackward, as in that actingforward, we must do what is shewn in the partsrorsoffig. 4: we must have apairof V wheels on the same shaft, with the power of turning one of them in reference to the other; and then connecting them by proper screws, &c. to preserve the position thus given: by which means, in a word, all shake orbacklashwill be completely annulled.
PART FIFTH.A NEW CENTURY OFInventions.
A NEW CENTURY OF
Inventions.
This Machine is not, generally, anarithmetical Machine. It pointslower: and therefore promises more general utility. Though less comprehensive than machines which perform all therulesof arithmetic, it is thought capable of taking a prominent place in the counting-house, and there of effecting two useful purposes—to secure correctness; and thus, in many cases, to banish contention. It is represented infigs. 1,2,3, and 4ofPlate 42, and infigs. 3 and 4ofPlate 43.
Adding machine
There are two distinct classes of operations which may be noticed in this Machine: the one that does theaddition, properly speaking; and the other that records it by figures, in the very terms of common arithmetic. The first operation is the adding: which is performed by means of an endless geering chain, stretched round the wheelsA B C D, (fig. 1) andoverthe two rows of smaller pulleysa b c d e f g h i; where, observe, that the chain is bent round the pulleyA, merely to shorten the Machine, as otherwise the keys 1 2 3, &c. to 9, might have been placed in a straight line, and thus the bending of the chain have been avoided.
The chain, as before observed,geersin the wheelsBandD, which both have ratchets to make them turn one way only. Now, the keys 1 2, &c. have pulleys at their lower ends, which press on the aforesaid chain more or less according to thenumber it is to produce, and the depth to which it is suffered to go by the bed on which the keys rest, when pressed down with the fingers. Thus, if thekey1 be pressed, as low as it can go, it will bend the chain enough to draw the wheelBroundone tooth—which the catchEwillsecure, and which the wheelCwill permit it to do by the springFgiving way. But when the key 1 is suffered to rise again, this springFwill tighten the chain by drawing it round the pulleysAandD, thus giving it a circulating motion, more or less rapid, according to the number of thekeypressed. Thus, the key 5 would carryfiveteeth of the wheelBto the left; and the catchEwould fix the wheelBin this new position: after which the springTwould tighten the chain in the same direction and manner as before. It is thus evident, that which-ever key is pressed down, a given number of teeth in the wheelB, will betakenand secured by the catchE; and, afterwards, the chain be again stretched by the springF. It may be remarked, that, in the figure,allthe keys are supposedpressed down: so as to turn the wheelB, a number of teeth equal to the sum of the digits 1, 2, 3—to 9. But this is merely supposed to shew the increasing deflexion of the chain, as the digits increase: for the fact can hardly ever occur. We draw from it, however, one piece of knowledge—which is, that should the eye, in computing, catch several numbers at once on the page, the fingers may impress them atonce on the keys and chain; when the result will be the same as though performed in due succession.
Elevation of key
Thus then, the process ofadding, is reduced to that of touching (and pressing as low as possible) a series of keys, which aremarkedwith the names of the several digits, and each of which is sure to affect the result according to it’s real value: And this seems all that need be observed in the description of this process. It remains, however, to describe the5th. figure, which is an elevation of theedgeof the keyboard, intended to shew the manner in which the two rows of keys are combined and brought to a convenient distance, for the purpose of being easilyfingered.
Adding machine
We now come to the other part of the subject—that of recording the several effects before-mentioned. The principle feature in this part, is the System ofcarrying, or transferring to a newplace of figures, the results obtained at any given one. This operation depends on the effect we can produce by one wheel on another, placed near it, on the same pin; and on the possibility of affecting the second,muchless than the first is affected: Thus, infig. 3 and 4, (Plate 42,) ifAbe any tooth of one such wheel, placedoutof the plane of the pinionB, it will, in turning, produce no effect upon that pinion: but if we drive a pin (a) into the toothA, that pin will move the pinionBone tooth (and no more) every time this pin passes fromatob. And if we now place a second wheel (F) similar toA, at a small distance from it, so as togeerinallthe teeth of the pinionB, this latter wheel will beturned a space equal toonetooth, every time the pinapasses the line of the centres of the wheel and pinionA B, (say fromatob.) It may be added, likewise, that this motion,of one tooth, is assured by the instrument shewn atE D, which is called in Frencha tout ou rien, (signifying all or nothing) and which, as soon as the given motion ishalfperformed, is sure to effect the rest: and thus does this part of the process acquire, likewise, a great degree of certainty—if indeed, certainty admits of comparison.
Addign machine
It is then, easy to perceive, how this effect on the differentplacesof figures is produced: and it is clear, that with the chain motion just described, it forms the basis of the whole Machine. There is, however, one other process to be mentioned, and as the2d. figureis before us, we shall now advert to it. In adding up large sums, we have sometimes toworkon thetens, sometimes on thehundreds; which mutations are thus performed: The wheelB, (fig. 2) is the same as thatB,fig. 1; and it turns the square shaftB G, on which the wheelsk lslide. The wheellis to our present purpose. It isnowopposite the place of shillings; but by the slidem, it can be successively placed oppositepounds, tens, hundreds, &c. at pleasure: on either of which columns, therefore, we can operate by the chain first described—the wheelBbeing the common mover.
Carrying machanism
We shall now turn tofigs. 3 and 4ofPlate 43, which give another representation of the carrying-mechanism, adaptedespecially to the anomalouscarriagesof 4, 12, and 20, in reference to farthings, pence, shillings, and pounds, andthenfollowing the decuple ratio.
Infig. 3,k lrepresent the two acting wheels of the shaftB G,fig. 2; the latterdotted, as being placedbehindthe former; these wheels, however, are not our present object, but rather the carrying system before alluded to; and described separately, infig. 3ofPlate 42.A, infigures 3 and 4(ofPlate 43) is the first wheel of this series. It has 12 teeth withthreecarriage-pins (or plates)a, which jog the carrying-pinionB, at every passage of 4 teeth; thus shewing everypennythat is accumulated by thefarthings. This is so, because the farthings are marked on the teeth of this first wheel in this order—1, 2, 3, 0; 1, 2, 3, &c. and it is in passing from 3 to 0, that this wheel, by the carriage-pinionB, jogs forward thepence wheelCone tooth: But this pence wheel is divided into 12 numbers, from 0 to 11; and has on it onlyonecarrying-pin (or plate)b; so that, here, there is no effect produced on the third wheelD, until 12 pence have been brought to this second wheelC, by the first, or farthing wheelA. Now, this third wheelD, is marked, on it’stwentyteeth, with the figures 0 to 19, and makes, therefore, one revolution, then only, when there have been twenty shillings impressed upon it by twenty jogs of the carriage-pinb, in the second wheelC. But when this wheelDhas made one whole revolution, it’s singlecarriage-pinc, acting on the smallcarriage-pinion, like thatc d, (but not shewn) jogs forward, by one tooth, thewheelE, which expressespounds; and havingtwocarriage-pinse f, turns the wheel calledtens of pounds, one tooth for every half turn of this wheelE: and as, on all the succeeding wheels, to the left fromE—(seefig. 2,Plate 42) there are two sets of digits up to 10, and two carriage-pins; the decuple ratio now continues without any change: and thus can we cast up sums consisting of pounds, shillings, pence, and farthings, expressing the results, in a row of figures, exactly as they would be written by an accountant. The opening, through which they would appear, being shewn infig. 1, at the pointw, corresponding with the linex yoffig. 2in the samePlate.
I shall only remark, further, that thefigures 3 and 4inPlate 43, are of the natural size, founded, indeed, on the use of a chain that I thinktoo large; being, in a word, the real chainde Vaucanson, mentioned in aformer article: and that the figures ofPlate 42are made to half these dimensions, in order to bring them into a convenient compass on the Plate.
I would just repeat, that I have not attempted here an arithmetical machine in general; but a Machine fit for the daily operations of the counting-house; by which to favour the thinking faculty, by easing it of this ungrateful and uncertain labour. Had I been thus minded, I could have gone further, in a road which has been alreadytravelledby my noble friend the late Earl Stanhope, (then Lord Mahon) but I took a lower aim; intending in the words of Bacon—“to come home to men’s business and bosoms.”
Rotatory punch machine
It is highly desirable, (not to say indispensable) in the use of my engraving Machine, to have punches not only of the true cylindrical form, but exactly of the proper length. (See the remarks on this subject, in the description of thatMachine). It is, therefore, a matter of consequence, to be assured that both these circumstances unite; and to unite themwithoutdepending on personal skill, whenever the work can be accomplished without such dependence: and this is the object of the present rotatory Punch Machine. Adverting first to the length of the punch:thatis insured by having a kind of slide on the Punch Machine, formed like thefrogspoken of in the above article—Engraving Machine. In the5th. figureofPlate 43, this slide is shewn ata, and it is at exactly the same distance from the centre of motionA, as the bottom of the frog-platefig. 3Plate 39is fromit’scentre of motion. Thus, the bottom of the punch is filed straight, once for all, and being fixed in proper clams, as in the figures, the shaftAis set a-turning, by power—from which motion two uses are derived: first, the cylindrical form is given to the punch by presenting to it, in it’s revolution, afileduly wedged on the (now fixed) slide of the MachineB B; against which it is keptturning, till, by a due depression of the centreA, the radius is brought to the length required, and the surface perfectly formed and smoothed. This being achieved, the camsc d, are fixed to the slideB B, and to the turning bodyA d, so that when the diefis moved toward the left hand by the said cams, the prepared punch gently presses on it, and begins to receive it’s impressions; which are gradually deepened by the set screwsg h,fig. 6; till, at once, the proper radius is given, and the engraving sufficiently transferred from the die to the punch—an operation which this process is calculated to perform, rather by means of frequent and gentle contacts, than by slow and heavy pressure. It need not be added, that the motion of the slideB Bis reciprocated by the springC, against thatD, after each forward motion given to it—asbegunby thecamsc d, and continued by the contact of the die and punch, all which a mere inspection of the figures will sufficiently explain. It is likewise evident, that thefigs. 5 and 6, shew, both, the same objects, namely:—the regulating wedgesi k, the upper set screwsg h, and the rollersE, on which the slide vibrates during the operation of the Machine.
Pedal driven pump
It is not solely because, to work with the feet is a good method of employing the strength of men, that this device is presented to the mechanical public; but it is with the view ofsoemploying the feet and hands, that they may occasion a constant andequableflow of water. The means, (seePlate 44,fig. 1) are, to provide the man with two supportsa bfor his hands, and two pedalsc dfor his feet, by which the two rodse fare worked; and by them, through the cords or chainsg h, the piston rodsiandk. Of the latter, the one which answers to the lower pumpl, goes through the upper piston, whose rod isi: and the pistons are both constructed in the manner shewn infig. 2; that is to say, the piston has nobody, fitting the pump barrel: but a triangular barx, going diagonally across the pump barrel, (which is square) and carrying two wings or valvesy z; which, both together, fill the barrelwhen down, and leave it as empty as possible when up, by which motion the chainsa eare slackened. Further, these pistons, with their rods, are heavy enough to raise the pedals, the instant the man raises his feet in any degree: so that, by a proper combination of the motions of his hands and feet, he can let down a given piston, and begin again it’s ascending motion before his effort has wholly ceasedon the other pedal. A mean this, of producing a constant and equable rising motion in the column of water through the pumpsk l; and a mean also, of doing more work with a given fatigue, than would bepossiblein a pump whose motions were merely reciprocal, and the water of which, in rising, would be subject to any unequable or convulsive motions.
In general, this portable pump was made (many years ago) with a view to being easily carried to any field or garden, bordering on a river, and worked on it’s bank; the flexible suction pipepbeing thrown into the river, or a well, as occasion might require. To this end, the whole frame (as is evident from the figure) can be folded up into a kind offaggot: and thus it’s transport from place to place, be made perfectly commodious.
Itoftenhappens, that from a central line, (in drawing for example) we want to set off, quickly, many equal distances on each side; or between two given lines we want a central line; to perform either of which operations, is the use of the Instrument just mentioned.
Bisecting compasses
It is represented inPlate 44.figs. 3 and 4, whereA Bis the centralpoint, being cylindrical in the greatest part of it’s length, and conical atE B. It slides correctly in twocannonsor swivelsE&A, which also have two short axes or trunnions, on whichfirst, the double compass jointsC Dturn; and second, thetwopairs of armsF G. I have called these cannons,swivels, that I may shew their construction, by referring tofigure 1inPlate 30—which describes the swivel of theforcing Machine; and which will give a complete idea of what is here intended. From this construction it will appear evident, that the pointA B, (Plate 44) will be always found in the middle, between the two points, of the outer legs of the compasses; andthatwhether the question is to take two equal distances from a central point, or tobisecta given line or distance at one operation. The point or style nowslidesin the two swivelsAandE; but the Instrument might be so constructed, as forit to follow the rising motion of the middle joint (E), and thus to keep the three joints in the same horizontal line: but I think a small perpendicular motion of the saidstyle, would be always desirable in the Machine, as a drawing Instrument.
Adjustable pitch forl
This device is shewn, in two positions, atfigs. 1 and 2ofPlate 45. In it’s present application, it is intended to produce a whole octave on the diatonic scale: and therefore, the unsupported ends of the fork are just half as long as they would become if the sliding handleA, were drawn to the bottom end of the branchesc d. For, again, the fixing screwC, and it’s boxDare fastened to this sliding handle by one or two screws, (s) so as to be always ready to press the branches against the enclosed slideA B, at whatever place the intended tone may be found. Now, the branchesa c,b d, spring out of a common trunkc d, which is pierced with a square hole, exactly fitting this sliding handleA B; and the latter is marked, at proper distances, with lines across it, each of which (placed opposite the markc d) gives such a length to the remaining branchesa b, as to make them sound the note desired. Thus, the line l, brought toc d, lengthens the branchesa b, to (nearly) 53 parts, from 50 at which they arenowfixed; the whole lengtha c, being 100. This, and the following divisions would, of course, follow any desiredtemperament, according to the will of the tuner: but I have supposed them founded on the equi-harmonic scale; and thus willthe successive intervals to be set off on the slideB A, be as follows: (while the corresponding notes will be those expressed in the table.)
In the state represented by thefigures 1 and 2, the line aB, is 5000; being one half of the whole lengtha b,c d.
The above lengths 1 2, 2 3, &c. have been measured off on the slideA B, as nearly as possible, or at least with precision enough to give the idea: and the rest I must leave the detail of, to those musical readers who may feel interested in the subject.
I have done right in calling these attempts “essays”: and if I had said “immature attempts,” they would have been better designated. Yet, having promised them to my readers, I cannot now withhold them, although, from want of opportunity of trial, I can do little more thantalkof their supposed properties.
First essay
The first essay, as shewn infig. 3ofPlate 45, is amental deductionfrom a device which I executed in 1801, and brought before the public at the exhibition then given, by the French government, of the produce of nationalindustrie. It was, nothing more than apendulum, made with a view to lengthen, considerably, the going of a given clock, without altering the wheels. To that end, the weight or bob, was a heavy barC D, suspended diagonally on two pointsA B, placed at a distance from each other, exactly equal to the length of the said bar: andthatby the double cross-barsB CandA D, of a length sufficient to make the whole assume a form exactly square: where it may be noted—that were this figurelongerthan high, the curve of vibration would have two points of inflexion, and the barwould notplace itself horizontally at last; and that were it narrower andhigher, that curve wouldassume a form more like, though still distant from, the arc of a circle. In the present case, such was the effect of this disposition of things, that the centre of gravity of the bar described, in vibrating, a curveE C D F, the lower form of which, was so near to ahorizontal line, that thetimesof vibration were immensely prolonged; so much indeed, as to represent a common pendulum of several thousand feet in height; and to give a proportionate slowness to any mechanism with which it should have been connected. In fact, this line is so minutely different from such horizontal line, that it is wholly included in the thickness of thedrawn-lineC D: nor becomes visible but near it’s two endsC D, when it begins to rise, andthenrises faster than that described by ashortcommon pendulum.
In fine, this curve itself is formed by continually bisecting the line or barC D, and drawing lines from it’s centre of gravity, thus found in one of it’s positions, to the same in another position, till the curveE C D, &c. arises from this process.
It follows, then, from the nature of this curve, (or pair of curves) that the time of vibration of this pendulum is thelonger, theshorterthe arcs are, in which it vibrates; and that, when the vibrations have attained a certainlength, compared with the height to which the centre of gravity rises, thetimebecomes considerably shorter. I shall not now pursue this idea, because it is at once an abstruse question, and at the same timeone of uncertain utility—I mean that it’s use is problematical as a pendulum: since thetimeof a vibration depends on it’slength, which cannoteasilybe determined by any invariable method. I shall, however, add two things on this subject, by way of land mark; the one, that the balance-wheel of a watch has power enough to drive this pendulum, heavy as it is;—and the other, that I haveseenit make (for many hours together) vibrations ofhalf a minute’s duration!In a word, this is one of the subjects, which untoward circumstances have prevented me from bringing to maturity—but which I owe to my subscribers, and the public, in any, or every state, to which I have brought them.
I therefore, say nothing more of this Instrument as a pendulum: but an inspection of thefigurewill shew, that it will not be useless as anElipsograph—which it clearly is, since the intersection of the barsA D&B C; describes a true Ellipsis. It may be further shewn, that the ends of the moveable barC D, are the vibratingfociof a second ellipsis, like the first, which rolls under the other, so that the curve itself isthatwhich the centre of one ellipsisa b cwould describe, by rolling on the surface of anothere b d. But, into these considerations I cannot now enter, as my “Century of Inventions” is fast becoming due, and time commands dispatch; I beg leave, therefore, to pass to the relation this subject seems to bear to a “Marine Level.”
It must, however, be premised, that I scarcely expect either of these methods to be correct enough for astronomical observations; as among other things, they have thenautical topto contend with: but if I am fortunate enough to have suggested useful methods of procuringrelativestability on board a rolling ship, so as to suspend the better, aniceinstrument of astronomy; or so to counteract the restless ocean, as to assist the victims of sea-sickness, I shall not entirely have lost my labour.
My first idea on this subject, is the following: If we had on ship-board, a simple pendulum of several thousand feet high, it appearscertainthat the oscillations of the ship would be begun and ended, before any single vibration could have been given to such a length of pendulum—which therefore, would scarcely vibrate at all: and if the naturaltimeof this compound pendulum (for we are not confined to these small dimensions) were made to be much longer than those of the shipon it’s meta-centre, this pendulum would scarcely vibrate at all: because it’s several tendencies to take motion from the ship, would extinguish each other before they had had time to produce any common effect.
Construction
Further, this result would probably be assisted by another property belonging to this mechanism: seefig. 4. This diagonal suspension, as repeated ata b c d,fig. 4, is of such a nature, that when it’s centresa b, are placed in anyoblique positione f, (say by the rolling of a ship) the suspended barc d, immediately takes a position of opposite obliquityg h, pointingupwardtowardsi, just as much as the linee bpointsdownward; while the middle linek lremains level—whether caused by the slidesk l, or the single slidem.
I dare not assert any thing respecting the form this principle should assume, in order to produce the most useful effects; but it appears that the principalweightof the apparatus should be placed in the centre of gravity of the under barc d. It would occur, of course, to every mechanician applying this System to real use, that in thisfig. 4, we have only provided for one motion of the ship, therollingmotion: and that, in consequence, this System should be suspendedinanother similar one, acting longitudinally, so as to provide for thepitchingmotions of the vessel. In a word, I confess, with regret, that I leave muchto do, by way of bringing this idea to maturity—it being at this late hour, more than doubtful, whether I shall myself ever be able to resume the subjectat sea, where alone it can be duly tried.
This would seem to be a simpler process than the former: but how far it may go beyond it in effect, I cannot say—having never had it in my power totryeither of these ideas on ship-board. I therefore merely present them to my readers, as themes for future thought and experiment.
Another level
Plate 45,fig. 5represents this System—which is founded on the idea of deadening oscillatory motions at sea, by connecting the bodies to be thusguarded, witha stream of flowing liquid, the horizontal motions of whichmust besubject to laws very different from those which rule vibrating bodies merely suspended.
The fluid used in this Machine (as oil, water, mercury, &c.) is to be pumped up by appropriate mechanism, from the vessel into which it flows atx, into a vessel placed a little abovez; and to be let out by the cocky, through a kind of strainers, of sufficient collective area to supply, with ease, the descending columnC. The vessel and tubeC Dare made as thin and light as possible: and the upper part, which is spherical, is inclosed in and suspended by the universal jointa b c, likethose used to suspend other bodies, as a compass, &c. Moreover, the areas, at different heights, of the tubeC D, are made in the inverse ratio of the velocities of the spouting fluid, at each given depth—so as to leave it but little tendency to press either outward or inward, while thus obeying the law of gravity. By these means, then, I think no vibrating motion will be excited in the falling column: but that the liquid will continue to flow perpendicularly, so as to preserve (nearly) the quietude of the vesselC D, and of any mirror or instrument it may be wished to keep in a given position, by connecting it with the perpendicular line thus obtained.
I repeat, however, that I know not how far these methods may go towards obtaining an artificial horizon, for astronomical uses. Indeed, I fear they will fall short in this respect—but I think them still worth trying, even for these—but especially for the purposes to which I have already alluded. And, if success crownsthis publication, to the degree I am led to anticipate, I will not always leave so rich a question, in this doubtful predicament.
This is a recollection from the specification of a Patent which I took out above thirty years ago, and in which I huddled together as many objects as a child would like to see in a box of play things. I perhaps acted, then, according to thewordsof a French proverb—“abondance de bien ne nuit pas;” but in so doing, I fell into the charybdis ofanotherFrench proverb—“qui trop embrasse, mal étreint,” (a wide embrace cannot be a strong one) and in so doing, paved the way to much litigation—which happily did not occur.
Fire escape
The intention of this Machine, as represented inPlate 46,fig. 2, was to retard the fall of anybody, or person, suspended to it, so as to prevent any concussion on reaching the ground. The means are brought to view in the perspective sketch given of the Machine. It is a kind ofjack, inclosed in a case, and supposed to be laid carefully aside in the house represented infig. 1of thisPlate. The Machine has a barrel, much like that of the jacks used for roasting; round which a rope is coiled, of sufficient length to reach the ground: and a wheel, connected with this barrel, works in an endless screw, which turns a shaft also like that of a common jack,but somewhat stronger; and finally, to this shaft is fixed a small cross piece, carrying, on pins, two weightsy z, inclosed in thefixedbarrelx; by the centrifugal force of which enough friction is created, to prevent the acceleration of the falling body—whether a person or weight of any kind.
There is, moreover, a jiba,fig. 1, fixed between some, or all, the windows of the house whose inhabitants it is wished to guard from the danger of fire; this jib having the property, from the form of it’s foot, of taking by the suspension of any weight to it, a position perpendicular to the wall: Insomuch, that by the act of suspending the Machine to the jib—engaging the wrist in the noosen, and perhaps the foot in another loop of the same cord; a person may safely flee those dangers from fire, of which so many persons become the unhappy victims.
Since the46th. Platewas engraved, it has occurred to me, that a method should have been shewn for raising the cordn, (fig. 2) after each descent. This operation might be performed by a handle put on the axis of the Machine, accompanied by a ratchet on the wheel, just like the similar parts of a jack for roasting. But, lest the inmates of a house on fire, should not have presence of mind enough to perform this operation, it might be better to have a spiral springinthe Machine, to bewound upby the descending body, and of force sufficient to raise again the cord after such descent.
This Machine is also shewn inPlate 46, atfig. 1. It consists of a large truck,A, to be drawn rapidly to anyhouse on fire, by one or more horses. The carriage or frame partB B, is anopensquare framesubtendedby a first sheet of sack cloth, similar to the sacking of a bed: and on this are laid five, or more,air mattrassesmade of sack cloth, and varnished on the inside so as to be nearly air-tight; I saynearlyso, for it isnotintended they should form a spring capable ofreturningany object thrown on them. On the contrary, each of the mattrasses has, at one or both ends, a valve 1, 2, &c. openingoutwards, but kept closed by proper springs, so as to determine the pressure at which the air shall escape; that pressure being carefully graduated, so that the upper mattrass shall give way with ease, the second with greater effort, and the successive ones with progressive difficulty, until the under one remains totally closed, and stops the falling body altogether. By these means, if enough mattrasses are used, and they aredulyregulated, a person may jump from a house of three or four stories without incurring any danger. As to the length and breadth of this fire-escape, it should be ample enough to givethe sufferers confidence to take the leap, and as small as an easy passage in the principal streets would require.
One thing must be described inwords—as the mechanism to which it relates is fixed under the truck; and could not be seen in this perspective figure. These mattrasses are filled with air by anhorizontal air pump, worked by acrank, which the axle itself of the hind wheels of the truck forms: whence, by pinning this axle to either of the hind wheels, the very motion of the carriage, as drawn by the horses, would distend the mattrasses—which would thus be ready for use the moment they arrived on the spot; and moreover, when there, this air could be replenished, after using, by turning this axle, through the wheels,by hand cranks slipped on it’s endsat the place of the linch-pins. Or, in fine, this operation might be performed by an air pump prepared for it alone, and placed in any convenient part of the Machine.