368 GEOLOGY OF OHIO. 
CHAMPION FAN. 
The larger the air-ways of a mine are made the greater the quantity 
of air is circulated with the same ventilating power; for the current is 
retarded in its progress by the friction which it encounters from rubbing 
against the sides, top, and bottom of the air-course. As it is not 
practicable to have large air-ways, owing to the difficulty and expense 
of maintaining them, it serves the same purpose to split the current into 
several parts, which, by reducing the velocity of the parts, reduces the 
frictional resistance to which they are exposed, and so, on the whole, 
produces a greatly increased current of air. The advantages of splitting 
air were well illustrated by Mr. John J. Atkinson, Government Inspec- 
tor of Mines, in a paper read before the North of England Institute of 
Mining Engineers, and published in vol. III of the transactions of the 
Institute. 
He shows that with a constant ventilating power, 16,198 cubic feet 
of air in one column will produce 70,884 cubic feet, in 5 equal 
and similar parts; 94,850 cubic feet, in 10 equal and similar parts ; 
99,722 cubic feet, in 15 equal and similar parts; 101,132 cubic feet, in 
20 equal and similar parts. 
Owing to the resistance offered by the shafts, says Mr. Atkinson, 
we dare not have more than a limited number of splits in a mine, 
because, although each split adds to the total quantity of air in cireula- 
tion, still in each separate split the quantity ultimately becomes less 
and less. | 
BIRAM’S ANEMOMETER. 
