662 GEOLOGY AND MINING INDUSTEY OF LEADYILLE. 



TABLE \ T I.Jlloicera in use. 



The horse power required to drive the blowers at a given rate is obtained by the 

 followiug empirical formula: V being the volume of blast in cubic feet to be deliv- 

 ered in one minute; P, the pressure shown by the manometer in the blast-pipes, 

 expressed in ounces per square inch ; H, the horse power ; aud Ji, the power required to 

 overcome friction, varying with the size of the blowers : 



_FxPx 0.003 



The power required to run one of the blowers is proportionate to the pressure of 

 the blast, volume delivered, and friction; blowers of different sizes require the same 

 power when they deliver the same volume of blast. 



Baker's rotary forced-blast blower These blowers are manufactured by Messrs. 

 WQbrshtta Brothers, of Philadelphia. They are compact aud constructed on very 

 simple principles. They deliver a positive blast, the volume of which is proportionate, 

 for each size, to the number of revolutions. They hardly ever get out of order aud 

 give universal satisfaction in Leadville. (The sketches corresponding to the followiug 

 description are those of a blower No. 5, taken from the maker's catalogue.) They 

 consist of a cast iron case, A (Figs. 1 and 2, Plate XLII), strongly ribbed and bolted, 

 rectangular in plan and section, and of an arched top, B. Inside of this works a drum, 

 D, carrying two tapering arms, G C", which sweep round so close to the interior periphery 

 that no air escapes. There are, besides, in the cast-iron case A two other drums, E 



