'266 PHILOSOPHICAL TRANSACTIONS. [aNNO 175S. 



XCVII. An Allempt to Improve the Manner of ^'Forking the Fentilators by the 

 Help of the Fire- Engine. By Keane Fitzgerald, Esq. F.R.S. p. 727. 



Dr. Hales wishing to extend his useful ventilators to those who work in mines 

 at great depths under ground, where the lives of many are lost by noxious va- 

 pours, occasioned by the want of a free circulation of air ; and finding by ex- 

 perience, that ventilators worked by wind do not operate above one third part 

 of the year, and in calm hot weather, when most wanted, do not operate at all ; 

 he applied to Mr. Fitzgerald for assistance in contriving a machine to work the 

 ventilator by the help of the fire-engine, which is now generally used in all mines 

 for drawing off the water : and which he accordingly attempted, and hoped it 

 would answer the purpose. 



As the lever of the fire-engine works up and down alternately, and performs 

 at a common medium about a dozen strokes in a minute, it was necessary to 

 contrive some way to make the beam, though moving alternately, to turn a 

 wheel constantly round one way, and also to increase the number of strokes to 

 50 or 60 in a minute. The model of a machine for this purpose is composed 

 of 4 wheels of diflTerent sizes, 2 clicks, 3 pinions, and a fly ; which is put into 

 motion by the part of a wheel fixed to the arch of a lever of the fire-engine. 

 The wheel which is turned by the lever, or rather moved up and down by it, is 

 loose on its arbor ; and likewise one of the rochets, and the wheel next to it. 

 The outside rochet and outside wheel are fixed on the arbor. There are two 

 pinion-wheels fixed on the arbor ; one on each side, near the edge of the wheel 

 moved by the lever which turns them. 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 

 3 times for each stroke of the lever, and may be increased or diminished, ac- 



