366 GEOLOGY OF OHIO. 
because at drift mines the fan and engine requir® the attendance of an 
engineer, as the furnace requires an atteadant. In a shaft mine the 
hoisting engineer can attend both engines, which is a saving of one man 
at the mine, besides the saving in the coal required to maintain a ven- 
tilating furnace. Whenever furnace ventilation is applied, the supply 
of air is liable to great irregularity by neglect of the furnace man; and 
the danger of fire, of which we have so many fatal examples, is ever 
present. Moreover, in mines where the furnace is placed at the bottom 
of the hoisting shaft, the guides, the ropes, and the timber of the shaft 
are subject to injury from the gases given off by the furnace. All these 
evils are obviated by the fan, in addition to the daily saving in fuel 
and attendance. 
The best ventilating tans are constructed on the centrifugal prin- 
ciple, and those of the Waddle, Schiele, and Guibal patterns, as already 
stated, have attained high fame in England and the continental states 
of Europe. Guibal’s is preferred to the rest, and is probably the best 
GUIBAL’'S FAN 
ventilating fan for the use of coal mines ever invented or applied in any 
country. This fan has a large diameter, some of those used at the deep 
and extensive mines in England ranging from 40 to 50 feet. The blades 
of the fan, eight in number, and 10 feet wide, are inclined backward, 
and the air is discharged through an adjustable shutter into an expanding 
chimney 20 feet in height; this fan, although more extensively applied 
