ON THE MECHANICAL EQUIVALENT OF HEAT. 
357 
The Ice Cooler. —(Part I., par. 19.) 
5 . Some preliminary experiments indicated that a length of about 200 feet of 
f-inch diameter lead piping would, when immersed in a mixture of ice and water, be 
sufficient to cool a stream of some 16 lbs. of water per minute very nearly to 
32° Fahr. 
The ice cooler was accordingly made as follows : A wooden box, 4^ 0 ^ X 2 3 X 2 0 , 
and lined inside with waxed cloth, was fitted with a horizontal wooden shelf about 
2 feet 6 inches long, and on this was laid a flat oval coil of |-inch composition piping 
nearly 200 feet in length, the left-hand end of the coil and shelf stopping short at a 
distance of 1 foot from the end of the box, the right-hand end of the coil reaching 
the end of the box, but the shelf stopping some 6 inches short of that point. The 
coil was about 5 inches diameter, vertically, and over it were placed the wooden 
guide plates shown (Part I., fig. 7). An 8-inch diameter paddle, having 6 wooden 
floats, was placed about the middle of the box, at a height just sufficient to ensure 
the lower edges of the floats clearing the coil of pipe below it. A galvanized iron 
wire netting, extending from the shelf upwards to the top, separated the well at the 
left-hand end of the box from the compartment to the right containing the coil and 
paddle. 
When working, the well and space beneath the shelf contained broken ice, well 
rammed in ; while the level of the water was automatically kept at about 3 inches 
above the top of the coil. The jiaddle, driven by a cord from the line shafting in the 
engine-room, revolved in the direction shown by the arrow, and caused a circulation 
of water ujo through the ice in the well, and then horizontally through the coil and 
back to the ice under the shelf. 
Circulating Pump. —(Part I., par. 20.) 
6 . In order to supply sufficient water to the brake against the resistance offered 
by the 200 feet of pipe in the cooler and the augmented pressure in the brake itself, 
it was necessary to use a circulating pump. This was a small Mather-Reynolds 
centrifugal pump with four 1^-inch wheels, driven by a turbine available for this 
purpose in the engine-room. This pump was capable of supplying 16 lbs. of water 
per minute, against a pressure of 25 lbs. per square inch at the supply valve. 
Some difficulty was encountered in the summer of 1896 with this combination, 
because the excessive demand for condensing water for the engine hardly left sufficient 
flow in the falling hydraulic main to work the turbine at the requisite speed to 
maintain the above pressure. 
On the whole, however, the combination was exceedingly efficient, and with a 
graduated supply valve afforded a very delicate means of regulating the flow of water 
into the brake, 
