Chapter XII: Introduction (5)

Thus, it appears, that the turning motion of the two sectors is the same; and that a given point of the lower one will always _visit_ the same point of the corresponding plane _s t_, independently of contact with any substance lying on it; and that, therefore, the pressure, though successive, is perpendicular, having _no_ tendency to displace or _pucker_ the paper laid on it; besides which, it may be observed, that the _power_ of this Press is immense, from the length of the radii of the sectors _E F_, and the absence of any _rubbing_ motion.

I observe, further, that _racks_, made with teeth on my principle, either singly inclined with cheeks, as in Plate 14, or with teeth in the V form, will produce a more certain effect than the cords and pulleys above described, provided the arcs _b c_, and the upper sector _E_, be prepared and toothed accordingly.

OF
A REFLECTOR
_For Lighthouses, &c._

The object of this Invention is to join economy of light with splendour of effect. The means are the following:--

From the nature of reflecting curves, it follows that the smaller a luminous point is, the more perfectly will its emanations be reflected; for a _focus_ is a point of the smallest magnitude, if, indeed, it has any dimensions. My idea, then, is to make a focus of a _line of light_ very minute in it’s _section_, but as large, in it’s contents, as may be desired: thus securing a considerable _fasces_ of luminous particles while using them in an economical manner. To this end (see Plate 28, figs. 3 and 4), I form my reflecting surface of two distinct parts, having a section common to both, viz.--1st. a concave-parabolic-spindle, represented at _A B C_, as cut by a vertical plane passing through it’s centre; and 2ndly, a parabolical bason _E D F G_ (represented in the same manner) surrounding the former, and so placed as that these surfaces have a common focus--namely, the _circular line_ of which _a b_ is the section; the line itself being shewn by an elevation passing behind the aforesaid _spindle_ _A B C_. This _linear_ focus, therefore, may be two or three feet in diameter; thus imitating the tenuity of a _punctual_ focus, while emitting a large quantity of rays.

This LAMP, then, consists of an oil vessel, which is formed by the outside of the parabolical bowl before-mentioned, surrounded, in it’s turn, by the cylindrical surface _P H_, _I Q_, this vessel communicating with the wick-ring _a N_, _b O_, by a passage, _H I_, made as thin as possible, in order to leave the light at greater liberty to pass downward after reflection. (Where it is proper to add that the _wick-ring_ is drawn too thick in the figure.) Now, it is well known that all rays of light issuing from a point, and falling on the concave surface of paraboloid belonging to that point as a focus, are reflected from it in lines parallel to each other; and, therefore, a great part of the particles emanating from the linear (or circular) focus _a b_, and impinging on the surfaces _F G A B_, and _B C D E_, will be reflected perpendicularly downward, as at _a_, 1 3; _b_, 2 4, &c. and this being the case all round the common centre _B_, there will be formed a cylinder of light of the diameter _H I_, diminished only by the shadows of the wick-ring, the passage _H N O I_, and the pillar _B L_, when _that_ is used, which is not indispensable.

If this cylinder of light strikes on the plane mirror _K H_, placed at an angle of 45° from their direction, these rays will be reflected horizontally, and, preserving their cylindrical form, may serve as a powerful _beacon_ to the benighted mariner; the more useful, because susceptible of those temporary variations of direction and aspect, long since employed to distinguish one station from another.

But, if it were desired to illuminate a large space at sea, or elsewhere, the aforesaid cylinder of rays would be received on a conical surface _K L M_, which would give it the form of an immense sheet of light, of a thickness (allowing for aberration) equal to the height of _P L M_, of the same conical surface.

I shall add only one idea--namely, that to light any round space, building, theatre, &c., this system might be made very efficient by throwing the sheet of light _M P_ higher or lower on the walls, &c.; or (altering the angle of the cone _K L M_) by bringing it down to any position in or below the horizon, as circumstances may direct.

It would be superfluous to say that this Lamp might be furnished with _all_ the advantages of the argand principle; or, the whole _wick-apparatus_ might be superseded by a circle of _minute_, and very numerous gas lights, forming, sensibly, the same linear focus; or a thin circular _slit_ might produce a real ring of light, strengthened by all the resources of this new and splendid discovery.

OF
A LONG PARALLEL MOTION,
_For Mangles, and other Reciprocating Machines_.

In the year 1793 or 4, I received _a written problem_, desiring me to give a plan of a _long_ Reciprocating Motion, that should be driven by the pit-wheel of a common water-wheel, of given dimensions, and placed in a given position. In a few days, I produced the drawing now represented in Plate 29. Its object, as required, was to move the cylinders _L M_, figs. 1, 2, 3, backwards and forwards, in the _long_ grooves or gutters _N O_, for the purpose of crushing or bruising their contents: but what those contents were I never knew. I, however, produced this Machine, considering it as a general thing, and of a nature to perform most operations of a similar kind. The Machine consists--first, of a long rack _I K_, much like a narrow ladder placed on it’s edge, and in the teeth of which work those of a pinion _p_, whose axis _q_ is connected with the wheel _r_, which receives it’s motion from the vertical wheel _s t_, which is the _pit-wheel_ in question. This communication takes place by means of an universal joint _x_, being a mean of permitting the pinion _p_ to vibrate from side to side of the rack _I K_, when arrived at either end of it. For example, the pinion _p_ now turns from left to right, and, being on the other side of the rack, and _held_ by the chain _v_, it drives the slide _P Q_ in the same right-handed direction, and, with the slide, the two heavy cylinders _L M_ before-mentioned;--for, the said slide _P Q_ carries across it’s middle the axle-tree _S T_, which is the centre of both these cylinders, and connects their motion with that of the slide now in question. Further, there are rollers placed between the cheeks _V V_, _on_ which the slide moves horizontally, as guided by other rollers, placed at the points 1, 2, 3, 4, &c. Again, the ends of the axle-tree _S T_ are furnished with two bow-like bridles, which, connected with the pulling bars _Y_, are again fastened to the slide _P Q_, at the two ends of the present figure.

When, now, the pinion _p_ turns (see fig. 1 and 3), the rack, slide, and cylinders roll in the grooves, till the end of the rack comes to that pinion; which, finding no more teeth, swings round the _last_, and taking a new position, reverts the motion, till the other end of the rack comes to it, and occasions another return: _ad inf._ This will be better seen at the third figure, which is an end elevation of a part of the Machine.--There, _P_ shews the slide and _one_ of the teeth of the rack (which teeth are longer than the rest, as seen near _L M_, in fig. 1.) In this figure, we see at _A_, a mass of brick-work, covered by the _sleepers_ 5, 6, 7, &c., on which the long cheeks _V V_ repose. There, also, the chains _v z_ are seen, connected with ring-bolts, which go _through_ the bars _a b_, and are _nutted_ on the other side of the spring-beams _c d_, in order to avoid the commotion which would otherwise attend every change of motion in the slide and cylinders. For this purpose, also, and especially to prevent any waste of power at these moments, there are _mixti-linear_ wedges laid in the gutters, such as are shewn at 6, which are formed so as to absorb the momentum of the cylinders, in exact conformity to the time employed by the pinion _p_, in swinging round the end tooth of the rack; and thus to save all the power and time possible.

OF
A MECHANICAL SYPHON:
_Which expels Part of it’s Water at the upper Level_.

An ordinary Syphon acts by the pressure of the air on the _upper_ water, which drives it into the ascending pipe, _because_ there is a (partial) vacuum made there by the weight of the falling water in the descending pipe; this being always longer than the first. Thus, in Plate 29, fig. 5, _A B_ shews the rising pipe of a Syphon, and _C D_ the falling pipe, which is longer, and sinks to a lower level _D_, than that _A_ of the water, which feeds the machine. _E_, in this figure, represents the vessel containing the mechanism on which the new effect depends: and which I shall now describe.

_B_ and _C_, fig. 4, are, one the ascending pipe _A B_ of fig. 5, and the other the descending pipe _C D_. They are surmounted by two cylinders, of unequal capacities--this inequality bearing a given proportion to the difference in the heights of the rising and falling branches of the Syphon. In each of the cylinders works a piston _a_, _b_, which, I think, need not be stuffed, but _well_ fitted. The large piston has proper valves in it, to let the water pass upwards, at all times; and the small piston has a valve _i_, opening upwards, by means of the mechanism we are now describing; and closing itself merely by the arrival of the piston into it’s present position; for the screw _c_ prevents the valve from rising higher: _e_, _f_, are two arcs belonging to the lever _E_, and being circles round it’s centre of motion. They are cut into teeth, on my Patent principle, and work in the racks similarly _toothed_, which give motion to the pistons _a b_, or receive it from them. Further, behind the stand _F_, common to both levers, vibrates, on a pin, another lever _g h_, the use of which is to _work_ the aforesaid valve _i_ in the small piston; and this it does, by means of the weight _h_, in the following manner:--The machine being supposed in the present state, the Syphon will act, as usual, through the valves of the large piston; and the water pressing on the small one, with a power proportionate to the excess of it’s column over that of the other piston (_a_), will raise the latter as fast as the piston _b_ descends; but the area of the piston _a_ being _larger_ than that of the piston _b_, there will be a pressure within the vessel _b c d a_, that _must_ expel (through any prepared aperture at the top) a quantity of water equal to the difference of area between the two pistons, multiplied by the stroke of both: the real quantity of which will ultimately depend on the difference of level between the higher and lower water; or between the lengths of the rising and falling branches of the Syphon, _B_ and _C_. When, therefore, this stroke is made, the end _h_ of the lever _g h_, which carries the ball, will touch the screw _d_, and stop the descent of the valve _i_, which will thus be opened; when the water will have free egress through the descending pipe _C_, and the piston _b_ will then rise through that water by the weight of the piston _a_, the valve _i_ being _kept open_ by the action of the weight _h_, until the piston _b_ has risen to it’s present position, when a new stroke is prepared, for the same reason as before: and thus may water be carried over a hill of (about) 30 feet above the level of any stream or pond, and dropped into a _lower_ canal on the other side, with the condition of leaving a part of that water upon the hill, proportionate to the difference between the level from which the water is brought, and _that_ to which it is carried.

OF
A FORCING MACHINE,
_For taking on and off the Cylinders of Calico Printers_.

The two figures, 1 and 2, of Plate 30, are intended to make this Machine known, assisted by the following description:--The first is a front view of it, and the other a partial view from above. In the former, _A B_ is the frame formed of, and firmly connected with the two columns _C D_, which are fixed strongly to the ground, at such a distance below the ends _C D_, as to place the aforesaid frame at the height of about two feet, or higher, if convenient.

In the two cheeks of the frame _A B_, are cast or bored two round holes for receiving the gudgeons of the _swivel_ _E_, one of which gudgeons is also seen at _E_, in fig. 2. This swivel turns in these holes; and it is itself perforated with a round hole just large enough to receive freely the body of the mandrel _F G_. This mandrel has now on it the cylinder, which is to be taken off. _I K_ are, moreover, two ears or studs cast or welded on to the top and bottom of the said frame _A B_, and at exactly the same distance from the centres of the swivel _E_ before-mentioned. These _ears_ receive the ring-formed ends of the bars _L M_; see also the bar _L_, in fig. 2. To these bars is firmly fixed the cross-bar _N O_, which forms the _nut_ of the screw _P_, by means of which the operation of the machine is duly _prepared_; for, now the cup _Q_ (in the centre of which the screw _P_ revolves against a proper shoulder) receives the end _G_ of the mandrel, which it presses forcibly, while the whole is in the position _E L_, of fig. 2; that is, when the two centres _E_ and _R_ form one right line with the bar _L_, figs. 1 and 2. To complete, then, the process of driving out the mandrel, the bars, mandrel and cylinder are, at once, strongly made to describe the arcs _a M b_, _a c_; the mandrel revolving round the centre _E_, which is that of the swivel and the bars round the stud _R_. But, in thus revolving, a given point of the mandrel describes the _quadrant_ _a M B_, and a contiguous point of the bars _L M_ describes the quadrant _a c_; insomuch, that the mandrel _must_ have been forced out of the cylinder in direction _G F_ by the distance _c b_; where we observe that, at the beginning of this motion, the two curves _a b_ and _a c_ coincide in their movements, and only begin greatly to diverge from each other in the latter parts of these motions (see _M b c_.) The power, then, of this machine, when the cylinder sticks fastest to the mandrel, _is infinite_: and this power becomes weaker, and the velocity greater toward the end of the operation; that is, when the cylinder has slackened on the mandrel, and no longer requires to be driven with the same force as at the beginning. It may finally be observed, that the bars _L M_ are suspended by an oblique bar or chain _S N_ to the ceiling of the room just over the stud _R_ or _I_, which is their real centre of motion, in the above-described process.

OF
A SYSTEM OF MACHINERY,
_For cutting and trying Tallow by Power_.

The wheel _A B_, Plate 30, fig. 3, _was_ a horse-wheel, but may be a _first motion_ of any given kind. It is placed on the ground-floor; and over it’s centre is another shaft, having on it’s upper end a chopping block _C_, which revolves with the wheel _A B_, as turned from below. In this wheel, _A B_ geers a pinion _D_, driving the lateral shaft _D E_, which has two functions: the first to work the lying shaft _F_, and by means of the cams _G H_, to lift the contiguous stampers; and, by means of the knives _I K_, to cut the tallow on the revolving block before-mentioned. Over this block is fixed an oblique scraper, which takes the tallow as soon as it is cut, and pushes it down an inclined channel, placed at _C x_, into the boiler. The second use of the shaft _E_ is to turn the _mill_ _M_, (better shewn at fig. 4), which is let down into the boiler, in one stage of the process, and drawn out by the tackle _N_, when not wanted. The use of this mill is to tear the fleshy parts of the substance, while in the act of boiling, and thus to disengage the tallow with so much the less heat, in order that it may be so much the less coloured. Besides this machine, there is a grapple _L_ to be first used, which stirs the tallow in the boiler by the rotatory motion of the arm _x_. This position of the grapple would alone indicate what I have yet to observe--namely, that the boiler is a kind of ring, the section of which is the line 1, 2, 3, 4, and it’s depth 1, 2, or 3, 4. To prevent, still further, the fat from being burnt or coloured, the flue for the fire is conducted solely under the bottom of the boiler, as shewn by the dotted lines in fig. 5: the smoke or heated air being forced to make two revolutions under it, as indicated by the arrows in this figure, where we see more particularly the fire-place _F_ in close connection with the rising shaft of the chimney at _G_; and this is so, because, with so great a length of horizontal flue, the fire would not enter the chimney till it had been heated to a first degree. There is, therefore, an opening into the chimney at _a_, and the fire, in lighting, is suffered to escape directly from the fire-place into the chimney; by which means, continued a few minutes, there is draught enough created to make the fire take its useful course through the flue afore-mentioned. I may just observe, reverting to fig. 3, that _O_ shews the fire-place _in elevation_, and _p_ the entrance into the flue, which last is double under the boiler, as shewn in fig. 5. Finally, the 4th fig. shews an end view of the _tearing-mill_, before-mentioned; but here on a larger scale, _A B_ being a part of the side of the boiler.

OF
A WASHING MACHINE, FOR HOSPITALS,
_Which confines the offensive Matter till cleansed away_.

Doubtless, the salubrity of every place, where _many_ people are collected, would be much increased, if all impure exhalations were expelled as soon as formed; and this is especially true of those awful but sublime receptacles, provided by Philanthropy, for the sick, the wounded, and the dying! To assist in the work of purifying the atmosphere of these doleful abodes, was the object (30 years ago) of the VENTILATOR, presented in page 170 of this work. But, I conceive, that a share of evil, quite as great, resides in the putrescent qualities contained in or connected with the clothes, the bed-linen, the dressings, &c., of the inmates of an hospital; to whose sacred claims on the efforts of every good citizen, the present article is devoted.

This Washing Machine (see Plate 31, figs. 1 and 2) is a triangular (or square) box _A B_, furnished with a lid _a b_, so fitted, as, when screwed down, to be hermetically closed.--And, N. B., to facilitate _this_ operation, I use in it a particular kind of screw (invented for the _hose_ of fire-engines), which I shall now describe. I take a common screw, with it’s nut, and cut away the threads of both, at two opposite _quarters_ of their respective circumferences, so that the screw can _enter the nut to the bottom without turning_; and the stuffing between the shoulders is so well fitted, in thickness, as to secure the penetration of the threads of the nut and screw the moment the latter _begins_ to turn. There is thus a full quarter of a turn, in which the nut and screw will press as strongly as though the threads had not been cut away; and thus are _nine tenths_ of the time required to use a common screw _saved by this simple process_: and thus, then, I close the lid afore-mentioned.

This Machine is further composed of a wheel _C D_, and a pinion _E_, to turn it with, either by hand, or by any proper application of power. The wheel turns the box _A B_, and thus agitates the contents in a way not dissimilar to the operation of the dash-wheels of calico printers. But, again, this wheel and vessel turn upon _two hollow gudgeons_ _c d_; one of which is destined to convey cold water into the wheel from the reservoir _F G_, to regulate which is the use of the cock _f_: the stuffing box _e_ being made as _good_ as possible, in order to prevent all leakage, either of air or water. The second hollow axis _d_ serves two purposes: it gives a passage to the fetid matter of which the expulsion is desired, and conveys it through the cock _g_ to the _sink_ or _sough_ below _h_, _without any communication with the surrounding atmosphere_.

But we said this hollow gudgeon had a second use: it is to bring steam into the revolving vessel _A B_, from any proper boiler beyond _K_, when that part of the process requires it.--There are, moreover, two partitions _C D_, _l m_, made near the ends of the vessel, and pierced with many holes, in order to suffer the cold water to flow in, and the dirty water to escape, without choking up the respective passages: and, finally, at the eduction end of the Machine (see _n_, _o_, _p_, fig. 2), there are placed three pipes, reaching from the angles of the box to the hollow centre, and furnished, at those angles, with valves, opening outwards; which thus form a kind of hydraulic machine to raise this matter from those places to the hollow centre, and thus, after a certain number of revolutions, to expel it entirely.

The process, then, for cleansing the objects contained in the vessel _A B_ (including the condition of cutting off all communication with the ambient space,) is as follows:--

1st.--These objects are dropped into the vessel as soon as produced, and the vessel is filled, one half or more, with cold water from the reservoir _F G_. The things are then left to _steep_ in this bath for a day or two, or what space of time the periodical mutations of the house permit. By which operation _alone_, the miasmata are already much confined by the water, even though the lid of the vessel should be but partially shut: after which, this steeping operation may be continued, with the accompaniment of a few turns of the handle (_E_) to fully saturate every part of the mass. In the second place, a small stream of water is let through the cock _f_, and the wheel _C D_ is kept turning for a few hours, to discharge the cold water and the most offensive matter, through the cock _g_, into the sink: and, thirdly, the steam-cock _K_ is opened (that _g_ being shut), by which means steam is brought into the vessel _A B_, and the whole soon raised to the boiling temperature. This state of things is continued, as long as it is found necessary; the motion, of course, being also continued, and even accelerated, that the mass of objects may _fall_ from angle to angle, and be thus _well washed_--that is, well _finished_, if _plain_ things; and fully prepared for finishing, by hand, if of a nature to require close attention. And, finally, in many cases, the warm process may now be abandoned, and a new stream of cold water be injected, accompanied by a due motion in the vessel, so as to _rince_ the contents; and thus leave nothing to do for the laundresses, but to dry and mangle, or _iron_ them; where, it is plain, that no inconvenience can have arisen from this process, either to these persons, or to the other inmates of the house.--Hence, then, this Machine _has the properties announced--of confining the offensive matter until cleansed away_.

OF
A MACHINE,
_For propelling Boats, on narrow Canals, without disturbing the
Water_.

The application of steam-power, to the motion of boats on narrow canals, is, I believe, much impeded by the consideration that the agitation of the water injures their banks, and would finally destroy them. On the other hand, it is known, that to drive a vessel, by acting on a fleeting medium, such as water, we must, at once, submit to lose about one half of the whole power employed--that is, the power, armed with energy enough to produce the required velocity, must go through twice the space that constitutes the _way_ or progress of the vessel. This depends, however, on the size of the floats or paddles employed, compared with the section of the boat, as modified by the form of the prow; but it is difficult to employ a paddle so large as to suffer more resistance from the water than the boat itself; and, if they are found _just_ equal, the _loss_ of power is exactly one half of the whole. These, then, are the two difficulties which I hoped to avoid, by the method now to be exhibited.

The idea is this--To have a large and heavy wheel _A_ connected with a _long_ shaft _B_, reaching from the boat to the shore, and, turning that wheel _in_ the boat, to propel the latter, by means of it’s rolling motion, on the bank or track-way; or, in some cases, on a proper rack, placed there for that purpose.

The Machine itself is represented in figs. 3 and 4, of Plate 31; fig. 3 being a stern-view, and fig. 4 a side-view, both of the machine and the vessel. _C_ is an axis, placed along the vessel, and turned by _any_ convenient power--as a horse, a steam-engine, &c. On this axis, considered as the _first motion_, are fixed the two bevil wheels _b c_, from which the long shaft _B A_ of the rolling wheel takes it’s motion. The use of the two wheels _b c_, is to drive the boat in the same direction on whichever side of the boat the wheel _A_ may be placed; for this, of course, must follow the track-way, which is sometimes to the right and sometimes to the left of the vessel.--Between the two wheels _c b_, is a sliding block (or catch-box) _d_, in which the shaft _A B_ of the large wheel has it’s lower pivot, and by which it’s wheel _B_ is almost instantaneously shifted from one to the other of the vertical wheels _b c_: the catch-box _d_ being itself _worked_ by a lever, of which the end only is seen at _e_, fig. 4. In fig. 3, there is further shewn a rope or _stay_ _f_, which, fastened to the socket _s_, of the rolling wheel _A_, and fixed in the middle of the boat, at the greatest possible distance from it, serves to keep that shaft at or near an angle of 90 degrees with the boat’s side: so that (the vessel being _long_) it becomes easy by means of the rudder, assisted, perhaps, by _lee-boards_ to keep the _way_ of the boat in a line parallel to the shore, notwithstanding the tendency to veer outward, given by the wheel _A_, while acting on a point so far from the body of the vessel.

I further observe, that, in order to shift the apparatus, with a certain facility, from one side of the boat to the other, there is a mast _M_ placed ahead of the mechanism just described, which rises as high as the length of the main-shaft (but can be _lowered_ to pass a bridge, &c.), and to the top of which is fixed the block _g_, through which a rope passes from the foot of the mast to the above-mentioned socket of the wheel _A_. By this rope the wheel is hauled up till nearly ready to fall over the centre; when a push from below will complete that passage; and the wheel _A_, being afterwards _lowered_ by the rope _h i_, will soon find it’s proper position on the other side of the boat, as before anticipated. Where, it should also be remembered, that this shaft must have a joint and socket, to permit it’s being bent, to pass a bridge, &c.

Hitherto we have supposed this rolling wheel to act on the bank or track-way solely by it’s weight; but this is not our only resource; for this wheel might be made of a moderate weight, and be pressed down by a brace reaching along the boat, toward the head and stern (see _k l_, fig. 3.), and _hauled taught_ through an eye of the socket _s_; by which _manœuvre_ (the points _k l_ being lower than the centre _A_ of the wheel) the latter will be pressed forcibly downward, and cause that cohesion there, from which the boat is ultimately to take her motion.

And, as to the wheel _A_ itself, I have _not_ represented it in the very form I should wish it to have, because it can be sufficiently described in words. I should cast this wheel (if made at all in metal) as a _shell_, the outside of which would be what is really seen in the figure (at _A_), and the rim would have in it mortices, like those which are made for iron wheels destined to receive wooden cogs, and geer with cogs of iron. In fact, this would become a wooden-toothed-wheel, with its teeth roughly formed and placed, so as to occasion a small expence, and to be easily changed, when worn away by the friction on the track-way. Thus would, I am persuaded, a very moderate weight in the wheel, and as moderate a pressure from the braces _k l_, connect the wheel with the road enough to produce the desired effect, with a trifling _loss_ of the power employed. And thus might we navigate a narrow canal, with a great saving of expence; not to mention that other advantage of avoiding entirely that injury to the banks, which must attend every system of propelling the boats, founded on the agitation of it’s waters.

OF
A MACHINE,
_For working, swiftly, the Slide-valves of Steam-engines_.

The Slide-valve is an excellent substitute for the _hand-geering_ of steam-engines, from the simplicity of form which it introduces, and the certainty of it’s recurring effects. But it is, I believe deservedly, reproached with being too sluggish in it’s operation, at the very moment when _activity_ would be most desirable--namely, at the beginning of the strokes; insomuch, say some, that the _power_ of the engine is materially lessened by it. The fact is, that the _excentric_ (usually placed on the crank-shaft) is almost always moving, and with it the slide-valves also; which thus open by _slow_ degrees, when they should open by _rapid_ ones.

Without discussing the question further, I cannot refrain from introducing this application of the principle of my Parallel Motion, given in page 237; which appears to me greatly calculated to obviate these difficulties; and thus to leave the slide-valve in possession of all it’s own advantages, with the addition of those which have hitherto belonged exclusively to the Hand-geering System.

I have represented this Mechanism in figs. 5 and 6, Plate 31: where _A B_ shew the crank-shaft of a steam-engine, working by means of slide-valves, the place of the _excentric_ being at _a b_, in a line with the pulling-bar _e f_. Instead, then, of the usual connecting _frame_ between the excentric at _a b_, and the valve-lever at _g_, I use for the above purpose, a lever _e f_ terminated by an arc _o_, furnished (in the present instance) with _five_ teeth, and connected by the joint _e_ with the valve-lever _g_, in the usual manner. In the arc, which terminates this lever _to the right_, are the five teeth above-mentioned; and, they geer in the _ten_ teeth of the wheel _c d_, which will be seen (in fig. 6) to be on the same shaft with the spur-wheel _m_, itself driven by the spur-wheel _n_, of twice the diameter. This wheel _c d_, therefore, makes two revolutions for one of the crank-shaft: and, supposing it to turn in the direction of the arrow, it will first of all draw _upward_ the arc _o_, producing no effect on the valve-lever at _g_; but, when the tooth _r_ is arrived at _p_ (the tooth _p_ being then arrived at the entrance of the curve _q_), the wheel _c d_ will begin to draw the arc _o_ along with it, round it’s own centre; and, the teeth of the arc being kept in it’s teeth by the similar curve _q_, the valve-bar will be drawn from _g_ to _h_, in the course of _one quarter_ of a revolution of the crank-shaft _A B_. But, now, the tooth _r_ of the arc _o_ will be found at _s_: and, therefore, the further revolution of the wheel _c d_ will carry the arc _o_ downward toward _t_, until the tooth _r_ has reached the point _t_; that is, until the wheel _c d_ has made another half-revolution, and the shaft _A B_ another quarter; when, as before, the arc _o_, conducted by the curve _t r_, will again drive back the lever _e f_, till it comes into it’s present position: after which, their motions will be regularly continued. It is, then, evident, that the slide-valves are thus opened and shut, each during one _quarter_ of a turn of the crank-shaft _A B_; and thus they remain stationary during another quarter, and that, in two positions of said shaft diametrically opposite to each other. And thus have we a simple mean, adaptable to every engine, of giving it much of the advantage of the hand-geering system, while preserving _all_ that of the slide-valve principle. And, were it desired to lengthen the _interregnum_ of the opening motion, it would be done by making the wheel _c d_ smaller, and the ratio of _n_ to _m_ (see fig. 6) larger in the same proportion.

I observe here, however, that care should be taken not to make the valve motions _too_ rapid, nor the intervals between them too long; for, I consider one of the best properties of this motion to be, that it acts _like an excentric_; that is, slowly at first, most rapidly afterwards, and finishes as slowly as it began; which is a _precious_ quality in all reciprocating machines.

Finally, I would remark, that the two last _rounds_ in the rack of the arc _o_ might be rather larger than the intermediate ones, and turn, moreover, on pins, so as to suffer less friction when rolling on the conducting curves _q_ and _t_. There might also be a plate or cap rivetted or screwed over all the teeth, so as to strengthen each one, by the force of the whole, as is shewn in fig. 1, Plate 29; from which, as before observed, this Mechanism is deduced.

* * * * *

The foregoing completes the Third Section of my work: and gives an article beyond the twenty, first intended:--which I thought important enough to claim this distinction. I now beg leave to add a remark or two on the text and plates of this, and the Second Part, by way of clearing up some obscurities, that might otherwise embarrass my readers.

And, first, in fig. 1, of Plate 21, the receiving vessel _M_, erroneously _appears_ to form part of the wheel _D E_; but is, in reality, placed _before_ it, as in all similar cases.--And, further, a small deviation of the circular lines, in Plate 22, has set the plate and it’s description, in page 192, _at variance_; the difference between the lines _o p_ and _C q_ being _not_ “imperceptible,” as there stated. I wish, then, that the dotted radius _A o p_, in the said fig. 2, may be carried (or supposed) halfway between _p_ and _C_. Finally, in page 200, line 8, the 24th Plate is incorrectly called the 25th.

I shall conclude this Part, by an observation or two on the reception my System of Toothed Wheels, as described in this work, has met with--not intending to speak of the local difficulties I experienced at a former period. But, _here_, the interests of truth force me to break silence. The necessity I stood under of bringing out this work in Parts, has, at least, had one advantage: it has given me an opportunity of watching the workings of prejudice--not to say of envy,--and thus of neutralizing, in some degree, the effects of either: from which, however, I claim nothing but the _right_ of making my labours the more extensively useful, by making them better known. I have, then, to say that, among _a few_ other objections to the System, _this error_ has come from so respectable a quarter, that it would be unjust to Science, and injurious to truth, to let it pass unrefuted. It has been said, that “my wheels are a Chinese Invention;” and _this_ proof has been adduced of it--namely, a sugar-mill, from China, having it’s cylinders _fluted in a spiral direction_. Now, the fact is, it would have been difficult to give a better proof that the wheels are NOT a “Chinese Invention;” for two inventions are then only alike when they produce the same effect, by similar means. But here the effects intended are totally different. A sugar-mill acts in or near the plane of the centres; and one of it’s cylinders is not intended to drive the other independently of pressure between them. This is so true, that the rollers of many sugar-mills are not fluted at all. Besides this, my wheels exert no pressure in that direction; and if they did, they would not be cog-wheels. In a word, their action is _at right angles to the former_, and has an object of quite a distinct nature. These, then, are by no means the same machine; and, therefore, mine is not a “Chinese Invention.”

Here, however, I _beg_ not to be misunderstood! I should feel no regret at appearing on the mechanical stage, a few hundred years after so ancient and astonishing a nation as the Chinese! But, in this case, truth did not permit me to sanction, by my silence, this flagrant error.

Finally, an opinion exists, _somewhere_, that these wheels _will_ never be generally used, from the difficulty of making them; and this opinion has been expressed, apparently, with no very amiable feeling. But, amiable or hateful, the opinion is highly erroneous! It is so far from fact, that, in a competent manufactory, they can be made more cheaply than others now are; and _many_ persons are already calling for them from every quarter; nor is any thing wanted to insure their immediate prevalence but a _common_ degree of commercial energy.

PART FOURTH.
A NEW CENTURY OF
Inventions.

OF
A CUTTING ENGINE,
_For large Bevil Wheels and Models, on the Patent Principle_.

One of the most prominent subjects of this essay, if not the most important, is the System of Toothed Wheels, with which the second and third Parts were introduced, and which still claims a share of my readers’ attention. As hinted a few pages backward, it seems not enough for me to exhibit and describe the System, but I must defend it against repeated objections, on pain of seeing it’s utility delayed, and the public deprived of it’s real and solid advantages. I am _far_ from wishing to impeach the _motives_ of those who still nourish or express dissent, when they deign to bring reasons for so doing; but the mere opinion--“it won’t do”--expressed by a man of reputation, may impede, for a time, the progress of an useful discovery, and thus produce a public evil. This, then, is a result I am anxious to avert; as the present System _has_ many points of excellence, against which no insuperable objection _can_ be brought. Had I not declined, already, to name either the friends or enemies of the System, I might here appeal to persons who highly approve of it; and, indeed, who use it daily with manifest advantage. But, I forbear. If, by means of the Engines already given, and _that_ I am going to offer, it is proved, that the difficulty of making these wheels is _trifling_, compared with their utility, one important point will be gained: I shall not hear it repeated, “that the System cannot succeed, _because of the difficulties of it’s execution_.”

The present Cutting Engine is shewn in figs. 1, 2, 3, of Plate 32. It’s immediate use is to form the teeth of _wooden models_, for casting. These are previously _built_ as usual, and _lagged_ with _bay-wood_, of sufficient thickness to furnish the teeth, and leave a small thickness of _that_ wood behind or under them.--_A B_, in fig. 2, represents a wheel of this kind, ready for cutting;--mounted correctly on the centre pin _C D_, which latter is so formed as to be _fixable_ in any position on the table or bench _E F_. Under the wheel _A B_, there is a kind of _index_ _a b_, put upon the said centre pin _C D_, which, by means of the clamp and screw _b c d_, can be occasionally connected with the wheel _A B_ so as to turn it, when it is itself turned by the means hereafter to be mentioned. To proceed with the description: _G_ is a slide, moving horizontally on the bench _E F_, as seen at _f e_ fig. 3; this slide being the basis of the headstock _G H_, which contains the _perpendicular_ slide _H I_, itself the support of the cutter-frame _K L_, so constructed as to turn on it’s bolt above _I_, and take any proper position over the edge of the wheel or model _A B_. This slide, then, with it’s appurtenances _H I K L_, moves along the bench _E F_, as seen in fig. 3 at _f e_: and what gives it this motion, is, the screw _g_, furnished, purposely, with a left-handed thread, working in the _half-nut_ contained in the small frame _h_, which contains also a jointed _cap_, that can be lifted off in an instant, and the screw set at liberty. Moreover, the second use of this screw _g_, is to _be_ thus disengaged from it’s nut, and lifted up to about _i_, where it serves to push back the slide _G_ towards the wheel, without that loss of time it would occasion if pushed back by the working of the screw. The letters _M N_, shew another important part of the Machine, applying to the cutting-process. It is an inclined plane, sloped to the same degree as the bottom of the teeth of the wheel. (See the line _a k_.) This inclined plane, then, is fastened, in any proper place, on the bench _E F_, by the wedge _N_, _just_ like the puppet of a common turning lathe; and it passes through an opening in the slide _G I_, or rather suffers this to pass _over it_, as better seen at _M_, fig. 3. Furthermore, the slide _I_ (fig. 2), after gliding down this inclined plane _M G_, will have to be raised between each cutting: and that is the office of the workman’s hand acting on the lever _O P_, through the iron frame _Q M_, which is shewn at fig. 3, in another direction; and marked with the letters _Q l m_. In fine, the slide _G_ carries on each side of the Machine a pulling bar _n_, connected with the said slide, and with a smaller sliding piece _o_, the use of which is to hold a pin (seen in the figure, but leaving no room for a letter of indication), which _turns_ the wheel _A B_, by the plate _p_, as the slide _G_ recedes, and the cutter-system _I K L_ descends on the inclined plane before-mentioned. Having thus adverted to all the important parts of the Machine, we turn to fig. 1, for the purpose of shewing _what_ the plate (whose edge is seen at _o p_) means; and the effect it is intended to produce.

In that figure, let _B A c_ be the section of any wheel it is desired to cut on this principle. The width of the face of such wheel is shewn by the line _a b_; and _a c_ is called the _projection_ of that face, on the base of the cone of which the wheel _A B_ is a portion; it’s summit being at _C_. The line _e d_, shews _one_ of the spiral teeth with which the wheel is to be furnished; and I make it by this uniform process: The pitch of the wheel, whatever it be, is set off from _e_ to _f_: and that pitch is divided into _eight_ parts, (shewn here as _four_ on account of their smallness) while the width of the face _f d_, is divided into _nine_ parts, shewn here (for the same reason) by _four and a half_ divisions. This latter division is more numerous than the former, that the principle may be a little _overdone_; or that the teeth may overlap each other by 1/9 of the pitch: To which purpose, beginning the spiral line _e d_ at _e_, I move in the second circular line from _e_ to the second radial line _C i_, and draw _that diagonal_ which forms the first part of the curved line _e d_. From this second point, I go to the third circular line, taking also the third radial line, and drawing the diagonal. This I do until arrived at the fifth circular line, when I find myself likewise at the fifth radial line _C d f_. These four spaces thus gone over, represent the eight parts into which this part of the face _a b_ _would have been_ divided, had the figure been larger: and there remains a small division near _d_, equal to one half the others, through which the curve _e d_ is prolonged by a similar process; and this latter portion is what the successive teeth _overlap_ each other, as before stated.

Now, it will be seen below, that the needful _circular_ motion is given to this wheel, by a movement that takes place in a direction parallel to the base _a c B_ of this figure. The curve _e d_, must, therefore, be transferred from the surface of the cone, to this base _a c B_. To do this, I place a point of the compasses at _A_, and trace, with the openings _A a_, _A c_, &c., the six _quadrants_ included in the space _a c g h_, which are now the projections, on the base, of the circular lines _a b f d_ on the surface of the said cone. Here, a slight difficulty should be obviated: strictly speaking, this _projection_ would be horizontal, and, of course, invisible in this position of the wheel. But I have supposed the figure _a c g h_, turned ninety degrees downward, round the horizontal line _a B_, so as to make one representation suffice; and also to shew the connection of the lines _a b g h_, with those _f d a b_. The curve _k l_, is thus a _copy_ of that _e d_, only _shortened_ in the proportion of _a b_ to _a c_--that is, of the side of the cone _a C_, to the half-base _a A_.

To secure, then, the coincidence of the pitch, as set off on the circumferences _a f_ and _a g_, we must divide a similar portion of both into an equal number of parts, _e f_; and treat them, on the lines _a c g h_, as we did on those _a b d f_; by which means we shall get the curve _k l_, _the projection of that_ _e d_. And this curve _k l_, must be made part of a _plate_ _k l m n_ (about 1/10 of an inch in thickness), the use of which is as follows:

This Plate _k l m n_, is no other than that marked _o p_ in fig. 2; and it is there fixed to the index _a b_, directed to the central pin _C D_, as it is in fig. 1 to the centre _A_--insomuch, that the _pin_ shewn in fig. 2 near _o_, acting on the _sloping_ curve _k l_, will turn that index (and with it the wheel) by the very motion which draws back the slide _G_ (fig. 2), and lets down the slide _I_ on it’s inclined plane _G M_.

We may remark, lastly, that as the present Machine is adapted to _large_ models, it is not, now, provided with a dividing-plate, although the means of so doing are self-evident. On the contrary, the division dots are seen on the edge of the wheel _A B_, as is likewise one dot, near _b_, on the clamp _b c_, from which a given distance is set off to each of the dots on the wheel, so as to give the pitch required. By these means, then, the wheel is divided and cut, in _good_, if not in exquisite divisions; and all the teeth take their shape from the Plate _o p_ (or _k l m n_ of fig. 1), and are thus good, in that respect also.

To recapitulate the steps of this process--The workman stands behind the Machine, near _E_; and, working the screw with his right hand, draws back the slide _G_, (the _power_ then turning the cutter _r_ very swiftly) by which means, the slide _I_ glides down the inclined plane _M_, and the cutter, impinging on the sloping face of the wheel, cuts it to the depth _r a_; the shape of the tooth (by the turning of the wheel) being the spiral form _e d_ of fig. 1. It may be added, that the lifting lever _O_ permits this descent of the bar _Q M_, because it is suffered to fall lower than _now_ represented. Thus, when the slide _G_ is arrived near _h_, the tooth is finished; and the cutter leaves the wheel at _a_: after which, the cutter-frame and slide _I K L_ are raised by means of the lever _O_--the screw _g_ taken out of it’s _steps_, and the slide _G_ pushed back by it, until the vertical slide _I_ rests again on the inclined plane _M_, as it at first did. Nothing, now, remains to prepare for cutting a new tooth, but to change the division-dot, by the application of the gauge or compasses, from _b_ to the next point on the wheel; to do which, of course, the clamp _b c_ must be loosened and refastened by the thumb-screw _d_. I would just notice the 4th figure--to say, it is a sketch of one quarter of a bevil wheel; intended merely to shew the form and position of these teeth, and the general appearance of the System.

Finally, my readers will please to advert to what has been already said on the _forms_ of these teeth, and their uses: and recollect especially what was observed on the epicycloid, as applied to them. It will easily be perceived, that to _put_ that form on one of these teeth would be an almost hopeless attempt!--and, happily, it is not necessary. We can, however, by using the cutter _r_ with various slopes, and going several times through each _space_, cut _facets_ on the teeth, quite near enough to the theoretical form to make them work _well_ together; and, as before observed, nothing is wanting to make the teeth _perfect_, but to run them together with the wheels placed in due position.

OF
A CENTRIFUGAL DASH-WHEEL,
_For Bleachers, Dyers, &c._

To form a true estimate of the value of any new machine, it is necessary to examine the nature and operation of those that have been used before for similar purposes. And this is the more needful here, because the present _Dash-wheel_ is essentially good, both in it’s properties and effects. The only room left for improvement, seemed to respect the _quantity_ of work done by it: and this is, the chief point of comparison we shall establish in what follows:--