VOL. XXXV.] PHILOSOPHICAL TRANSACTIONS. 20p 



when specifically lighter than common air. He fixed the trunks to the 

 sucking-hole of the engine ; and by working the engine, drew out the foul 

 steams from every part of the receiver, as the trunks were applied to them 

 successively. 



Exper. 3. — Having filled with foul steams, and set upright, as in the first 

 experiment, the cvlindric open receiver, he applied the trunks to the sucking 

 part of the engine, with their open end near the bottom of the receiver. 

 Then, by pumping, the steams were all drawn downwards, and so out at the 

 top of the trunks at the engine ; whereas, in the first experiment, they were 

 driven out at the top of the receiver. 



Exper. 4. — Having set a candle in the cylindric receiver abovementioned, 

 without having filled it with steams, and let down the trunks into the receivei-, 

 below the flame of the candle, he laid the wet leather over the mouth of the 

 receiver, leaving about half an inch open, for the air to come in; notwithstand- 

 ing which the candle began to dwindle, and was ready to go out; but working 

 the engine with the trunks joined to the forcing part, the candle revived, and 

 burned, at last, as well as in the open air. On leaving off pumping, the flame 

 of the candle diminished again; but when it was ready to go out, it revived 

 again, on forcing in more air with the engine. 



Remarks on the Experiments. — When damps in mines are specifically 

 lighter than common air, they will be driven out of the mine by the first 

 experiment. 



When damps are specifically heavier than common air, they may be sucked 

 out by the second or third experiment. 



When a sough, or adit, is carried from a mine to any distant valley, to dis- 

 charge the water, or save the trouble of raising it quite to the top of the pit ; 

 then shafts, or perpendicular pits, are generally sunk from the surface of the 

 earth to the said sough, to prevent the workmen from being suffocated as they 

 dig the sough, and that at a great expence; but, by the 4th Experiment, fresh 

 air may be driven down to the workmen, to continue their breathing free and 

 safe, and to keep in their candles; by which means the expence of perpendicu- 

 lar shafts will be saved. 



It has been found by several experiments, that a man may breath a gallon 

 of air in one minute, and a candle of 6 in the pound will burn nearly as long 

 in the same quantity of air ; therefore the model only is capable of supply- 

 ing fresh air to one man ; and consequently, a large engine will abundantly 

 supply air for the burning of candles, and the working of a great number of 

 men in a mine. 

 ■ Fire will not do in all cases, though in some, it will draw foul air out of 



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