216 
theoretical quantity of air which would pass through the fan 
each revolution. The fan makes 110 revolutions per minute, 
and is worked by the pressure of a column of water 450 
feet high, acting upon the piston of a small hydraulic engine, 
working in a cylinder four inches diameter and one foot 
stroke. The engine makes 20 double strokes, consuming 
211 gallons of water per minute ; so that the power expended 
to overcome the friction of the machinery and propel the air 
is equivalent to the weight of the above quantity of water, or 
215 lbs. falling through 450 feet per minute, equal to three 
horses' power nearly. The engine is considered not suffi- 
ciently powerful, and it is intended to increase the power ; 
but the passage of the air is also obstructed by a contraction 
between the fan and the upcast shaft, which will be remedied 
by a slant drift, nearly completed, for conveying the air 
direct from the fan into the upcast shaft. At present the 
circulation is increased by a fall of water issuing from an 
opening of five square inches area, and a head of three feet six 
inches from the top of the engine or downcast pit, which it 
is calculated discharges 120 gallons per minute. The com- 
bined effect of the waterfall and fan causes a circulation of 
27,700 cubic feet of air per minute. When the fan is not at 
work, the waterfall alone circulates 12,700 feet per minute, 
which leaves 15,000 cubic feet due to the effect of the fan. 
A comparison of the performance of the water employed in 
each case, and the power necessary to raise it again to the 
height from which it falls, will be as follows : — 
Gallons. Feet. Horse power. 
The fan uses per minute 21 J falling 450 ... 3 
The waterfall ditto 120 „ 450 ... 16 
Mr. Biram considered that this description of fan passed as 
large a quantity of air as any that he had seen. It might be 
fixed in any situation, and connected with any motive power, 
whether water or steam. Mr. Biram exhibited a beautiful 
working model of his fan, about a foot in diameter, the 
