4s, ORS Dp John Garric on the 
inches stroke, and, after —— the average space scene by 
the piston rod, of 206 cubic inches capacity. is pump was’ 
fitted with valves#ind communicated with the reservoir, in coy 
same manner as the larger pump. Its object was to charge the 
reservoir with air to any required tension before setting the larger 
pump and its antagonistic engine in operation, and thus save the 
enormous consum@#@#on of power which, it was supposed, would 
be required to work the larger pump so as to obtain the same ee ~~ 
ect. ‘Though theoretically necessary, it was found in practice 
that it could be advantageously dispensed with, and will not be 
introduced into any future construction of the machine. But as 
it was attached to it, and in most of the experiments to be here- 
after.detailed, its measure of air was condensed at every stroke of 
its own and the larger piston, its operation must be taken into ac- 
count in estimating the heat evolved by the condensation of a 
given volume of air. Added to the capacity of the larger pub 
(31444206 =) it made the whole quantity of air condensed b 
every stroke of the pumps or every half revolution of the engine, 
3350 cubic inches. 
The smaller pump, B, is also double acting, and of 56 cubic 
inches or one quart capacity. nds is designed to inject that quan- 
tity of cold water through the s F, F, and a sieve-like plate, 
or “rose”? placed in the upper lid, nae several perforations in the 
lower lid of the larger pump, and thence distribute it, in a finely 
divided shower into the interior of that pump. Its ‘object is to 
absorb the heat of elasticity set free from air by its condensa- 
tion, and at the moment of its generation, so as to lessen mate- 
rially the mechanical power that would otherwise be consumed. 
As it effects this object by mixing intimately the water and air, 
and causing the former to absorb the free heat, it renders the wa- 
ter an excellent approximate measurer of the heat evolved. After — 
-performing this office the water passes out of the pump, withthe _ 
condensed air, into the reservoir. 
he reservoir, or air magazine, C, employed in these experi- 
ments, is cylindrical in form, eleven feet in length, thirty-two 
inches in diameter, and has a capacity of about sixty-two cubic 
feet. It is made of sheet iron, with hemispherical heads, in the 
manner of a steam boiler. It is furnished with a safety valve 
about three inches in diameter, and loaded with a weight, through — 
the intervention of a lever. At one end it has a man-hole afford- 
ing admittance into its interior; and it is provided with a stop- 
cock, E, inserted into its most dependant part, through which the 
water of injection, received from the pumps, and precipitat ated 
. from the air by its greater specific gravity, may be dise into — 
the open atmosphere, or returned again to the pump, B, for bal 
pean of its duty. It is ot ag by three vineehe iron fi 
ich is represented at 
