There are also two clicks; one fixed to the great wheel, the other to the frame. These exclusive of the wheel that moves the fly. The effect is, When the lever moves the wheel downwards, its click forces the rochet fixed on the arbor to move along with it, and the other wheels the same way. When it moves upwards, the click fixed on the frame stops the larger rochet, and the wheel next to it, which are pinned together. This wheel being stopped, and the great wheel carried upwards by the lever, the pinion towards the edge of the great wheel is forced round it, and moves the pinion on the other side the great wheel; which pinion moves the wheel fixed on the arbor, the contrary way to the great wheel, which is carried upwards by the lever. By which means, the arbor is constantly turned the same way, when the lever of the fire-engine is moved either upwards, or downwards. Upon the arbor there is also another great wheel fixed, which turns a pinion: on the arbor of which pinion is a crank to move the ventilator, and also a fly fixed to the end, to help the motion of the crank, which in the model is turned three times for each stroke of the lever, and may be increased or diminished, according to the number of teeth in the pinion. The number of teeth in the great wheel moved by the lever is sixty-six; but need not have teeth above half way round. The wheel fixed to the rochet has thirty-three teeth, and its pinion eleven. The wheel fixed on the arbor, on the outside, has twenty-four teeth, and its pinion sixteen. The wheel, which turns the fly, has ninety teeth, and the pinion turn’d by this wheel ten. The greater the number of teeth in the rochets, the better. This machine may also be applied to other useful purposes at mines; and it may be easily made to turn a mill to grind corn; or to turn a wheel to raise coals, or whatever else is wanted to be raised from the mines. As I have not met with any thing of the kind described, I take the liberty of desiring you to lay it before the Society; and I hope it may be made some way useful to the public. I am, Sir, Your most obedient humble Servant, Kea. Fitz-Gerald. Poland-Street, June 7th, 1758. _Explanation of the Three Tables._ The wheel A (_Tab. 26._), which is turned by the lever B (_Tab. 27._), or rather moved up and down by it, is loose on its arbor; and likewise one of the rochets C (_Tab. 26._), and the wheel next to it D. The outside rochet E, and outside wheel F, are fixed on the arbor. There are two pinion-wheels G and H fixed on one arbor; one on each side, near the edge of the wheel A, moved by the lever. There are also two clicks _a_ and _b_; one _a_ fixed to the great wheel A, the other _b_ fixed to the frame. These exclusive of the wheel I, that moves the pinion _c_, on the arbor of which, the crank _d_, and fly _e_, (_Tab. 27._) are fixed.