On the Ventilation of Mines. 33 



tvl.lently that wliich will, in a given time, trnnsmit the greatest 

 r.uantity of air, with the least expenditure of pouer. Force of 

 blast, or co>npyes.s,o„;^re in this c-ase no object : mere ^mw,-- 

 tnmir.n is all that is required. The common bellows have been 

 proposed to extract from the mine, by a tube descending from 

 t.-^ v-alye ,nto the mine*. But here much power would be 

 uasted m rendering the blast forcible, and time ii, discharging 

 It. An air-pump with a i)iston has been also proposed ; but 

 against It the same objections are valid; beside the additional 

 xvaste o, power in overcoming the friction of the piston. A lar-e 

 vessel, or rather a number of vessels, inverted in a receptacle of 



lid ;•:. "",['"'■ f'^-' '""""'^ '^'''^ ^'''■'''''^ ^y •'»» ^^^^ revolving, 

 and hi.mshed with cranks, or otherv^se producing its effecT 

 would form a powerful blowing apparatus ' 



But the principle of the vl., or FANNER,-the winnowing 

 APPARATUS, seems free from all objections, and possesses the 

 greatest advantages. It transmits a great quantity of aii t^ 

 movement Ks rotative, and hence it can be attached to the -in 

 or gig employed in raising the minerals, and even placed on The 

 srane axis, so that tlie expense of construction will be trifling 

 It acts by a centruugal principle, and hence its powers of trans- 

 nutung air can be augmented to any assignable degree It is 

 only needud to increase the diameter of the circle and the powe 

 and to niake the entrance a.nl exit for the air of suitable capal 

 uty. It can leed either from one end of the axis, or from both • 



both ends to diflferent parts of the mine. The fan, as has been 

 said, may be placed on the same axis as the gin or gic., above 

 gl-ound, and wrought by the same power. It may be placed n 

 any convenient situation below, and wrought bv the power of 

 men, horses, asses or oxen. It may stand verticallv or horizon- 

 tally, and It may>../ hy numerous tubes extending to either 

 end of Its axis, from difJerent parts of the roof or floor of he 

 nnne, while It discharges into a spare shaft, or into the lower 

 end of tne shaft employed for liai.g the water, by one lar-e t Jbe 

 ex ending from the circumference^f the box containfeg tt 

 fan. In this way the expense of a tube would be saved by usinff 

 this Shalt; for the explosive gas, at least, being introduced intf 

 the bottom ol the shaft, would ascend by its own specific levity 

 Jhelun, toils employed, might oi,viate all danger both while tfie 

 |VT,rks are lormmg and afterward: and it is fitted to obviate aU 

 the mterrupt.on of ventilation from inequalities in the roof o' 

 floor of the mine. It is even suited to supersede the necessity 



• As fur as I know, tlils i<loa was first suL'pested by a Mr T) .vl.U,^.. 

 kct..^^on^_ natural philosopl.v. who haJ-^eeu b?i.::i b^.^l '^'^SJ- 



Vol. 48. Xo.219. J«/y isiti. C 



And 



