The effect is, when the lever B moves the wheel A downwards; its click _a_, forces the rochet E, fixed on the arbor K, to move along with it, and the other wheels the same way. When it moves upwards, the click _b_ fixed to the frame, stops the larger rochet C, and the wheel D next to it, which are pinned together; and as the wheel A is carried upwards by the lever, the pinion G towards the edge of it, is forced round the wheel D, and moves the pinion H, on the other side the great wheel A, which moves the wheel F fixed on the arbor K, the contrary way to the wheel A. By which means, the arbor K is constantly turned the same way, when the lever of the fire-engine moves either upwards, or downwards. The pinion G, by being made proportionally smaller than the pinion H, keeps the arbor K in the same swiftness of motion, when the lever is moved upwards, as downwards. [Illustration: _Philos. Trans. Vol. L._ TAB. XXVI. _p. 730_. _J. Mynde sc._] [Illustration: _Philos. Trans. Vol. L._ TAB. XXVII. _p. 730_. _J. Mynde sc._] [Illustration: _Philos. Trans. Vol. L._ TAB. XXVIII. _p. 730_. _J. Mynde sc._] The great wheel I, fixed on the arbor K, turns the pinion _c_, on the arbor of which the crank _d_ (to move the ventilator), and the fly _e_ (to help the motion), are fixed. The pinion _c_, is turned three times by each alternate motion of the lever; which may be increased, or diminished, according to the number of teeth in the pinion _c_. The number of teeth in the wheel A is sixty-six, but need not be toothed above half way. Instead of this wheel there might be a barrel, with a chord round it, fixed at each end of the arch of the lever, and projecting somewhat from it; which, by the motion of the lever, would work in the same manner in other respects, and be easier made, and at less expence. The wheel D fixed to the rochet C has thirty-three teeth, and its pinion G eleven. The wheel F fixed on the arbor K has twenty-four teeth, and its pinion H sixteen. The greater the number of teeth in the rochets, the better. _Tab. 26._ contains the plan (in parts) of the whole machine, except the lever B and fly _e_, which are in _Tab. 27._ _Tab. 27._ also contains the elevation of the arbor, with its different fixtures; _viz._ _Fig. 1._ The rochet C and wheel D (_Tab. 26._) fixed together. 2. The outside wheel F that works the pinion-wheel H (_Tab. 26_). 3. The two pinion-wheels H and G (_Tab. 26._) fixed on their arbor. 4. The same fixed to the wheel A (_Tab. 26._) by means of two cocks _u_ and _w_ (_Tab. 26._). 5. The arbor, with the wheel L and rochet E fixed; _t_ the place, where the wheel A is fixed. 6. The elevation of the whole arbor. _Tab. 28._ The elevation of the whole machine, the lever B (_Tab. 27._) working the wheel A (_Tab. 26_). _s_ (_Tab. 26._) a thin piece of metal screwed to the wheel A, to keep it in its place _t_ on the arbor K (_Tab. 27._)