S3(y YEIfTlLATION Ot MINES OJt IfOiPltALS. 



day light and even objects at its mouth were distinctly seett 

 from its farthest end. After blowing up the rock, the 

 miners could instantly return to the place where they were 

 employed, unimpeded by the smoke, of wliich no appearance 

 would remain underground in a very few minutes, while it 

 might be seen to be discharged in gusts from (he valve at the 

 top of the shaft. The constant current into the pipe at the 

 same time effectually prevented the accumulation of air 

 unfit for respiration. The influx of air, from the level into 

 the mouth of the pipe, rushes with such force as instantly 

 to extinguish the flame of a large candle; and any substance 

 applied, so as to stop the orifice, is held tight by the out- 

 ward pressure. 



It is now more than two years since the machine was 

 erected, and it has been uninterruptedly at work ever since, 

 and without repair. The length of the tunnel has been 

 nearly doubled, and the pipes of course in the same pro- 

 portion, and no waut of ventilation is yet perceptible. 



Two similar engines have been since constructed for other 

 parts of the same tunnel, and have in every respect an- 

 swered the purpose for which they were designed. 



The original one is worked by the small stream of water 

 before-mentioned, by means of a li^ht overshot-wheel twelve 

 feet in diameter, and about six inches in breast. — The two 

 othersare attached to the great overshot-wheel, which pumps 

 the water from the shafts which are sinking upon the line, 

 and as their friction is comparatively nothing, this may be 

 done in any case, m ith so little waste of power for this pur- 

 pose as not to be an object of consideration, even if the 

 power be derived from more expensive means. 

 Its appVicatkin The size of the exhauster may always be proportioned to 

 to various pur- ^y^^ demand for air, and by a due consideration of this cir- 

 cumstance, this engine may be effectually adapted not only 

 to mines and collieries, but also to manufactories, work- 

 houses, hospiials, prisons, ships, and so on. 



Thus, if it were required to ventilate a shaft of a mine, 

 or a singlejevcl, which is most frequently the case, where 

 three men are at work at one time, and we allow that those 

 three men vitiate each twenty-seven cubic inches and a half 

 gf air per minute, (as determined by the experiments of 



Messrs^ 



