MECHANICS AND USEFUL ARTS. 77 



the total resistances, then a mechanical ventilator, utilizing 60 per 

 cent, of the power employed, would, under tlie same conditions, 

 have a duty of 11 lbs. of coal per horse-power on the air, being a 

 saving of G4 per cent. At a depth of 550 yards to circulate the 

 same volume, the duty of the furnace being 22 lbs. of coal, that 

 of the mechanical ventilator would be 11 lbs., being a saving of 50 

 per cent." 



While on this subject we may also state that a machine has 

 been invented for the purpose of proper ventilation of mines, a 

 description of which we tali^e from the " London Mining Jour- 

 nal :•' — 



*' This subject has of late occupied the attention of mining and 

 mechanical engineers, as well as that of others who have been 

 startled into activity by the many appalling accidents which of 

 late have occurred in consequence of the explosive gases being 

 allowed to accumulate in mines. The question is, no doubt, one 

 of great importance, and they who shall succeed, either by me- 

 chanical or other contrivance, in keeping up a constant supply of 

 good wholesome air in all parts of a mine, will have conferred an 

 incalculable boon upon mining science. Hitherto, little provision 

 beyond the natural condition of things, or by adding a fire in the 

 shaft or bottom of the shaft, has been adopted ; and these, no 

 doubt, in small shafts, and in mines of very limited extent, have 

 been sufficient in determining a current by effecting thermometri- 

 cal variations. There is a degree of uncertainty about it, how- 

 ever, in consequence of the varying conditions of the external 

 atmosphere, changing as it does throughout the year. Hence 

 machines have been invented for the purpose of blowing fresh 

 air in and of exhausting foul air out of mines, some working by 

 means of ptimps, and others effecting the same object by means 

 of centrifugal action. Mr. Lloyd, the able engineer of the Lille- 

 shall Company, has been turning his attention to this, and he has 

 succeeded in inventing a machine of ingenious construction, 

 "which the company has patented. The success of the plan ap- 

 pears to depend upon the peculiar construction and disposition of 

 the fans, which beat the air out of the shaft, depending upon the 

 well-known elasticity of the atmosphere to supply its place. 



This he does by means of a centrifugal fan, driven by an en- 

 gine. The one we saw was a beautifully executed model, with 

 fan 18 inches in diameter and G inches wide over the blades, 

 which, measured by the aerometer, produced exhaustion at the 

 rate of 2,500 feet per minute, with a water-gauge of one-quarter 

 inch. But the company are erecting a larger one, to be worked 

 by a small horizontal, direct-action engine, which shall be de- 

 scribed when in ojDcration. It may be stated that the success 

 which has hitherto attended the trials made surpasses all expecta- 

 tion, and the effects produced appear incredible. He first made 

 a two-feet 3-inch fan, which exhausted 2,500 feet of air per min- 

 ute ; and another, with a 5-feet fan, one foot 10 inches broad, 

 which exhausted 25,196 cubic feet per minute, with a water-gauge 

 of two and three-eighths inches, Indeed, the effects were sucli- 

 as to be increflible to the inventor until after repeated mcasure- 



7* 



