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this Lamp might be furnished with all the advantages of the argand principle; or, the whole wick-apparatus might be superseded by a circle of minute, and very numerous gas lights, forming, sensibly, the same linear focus; or a thin circular slit might produce a real ring of light,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.