272 
POPULAR SCIENCE REVIEW. 
for evaporating the ether in the refrigerator, but pressure is 
exerted to liquefy the ether in the condenser. Both refrigerator 
and condenser are tubular vessels. Now, as the vapour passes 
from the refrigerator to be condensed by the pump, it is made 
to part with some of its chilliness either to ether going to the 
refrigerator, or to water about to be frozen ; and again in its 
return passage to the refrigerator it is deprived of any oil which 
it may have acquired from the machinery. The whole of the 
cooling apparatus is below ground, and contained for the most 
part in pits of cement or asphalte. The water to be frozen is 
run into metallic tanks, between the inner and outer surfaces of 
which chilled brine at a temperature of 15° F., or 17° below 
freezing point, is made to circulate, the metallic vessels being 
connected by stout vulcanized india-rubber tubing. The water 
during freezing is kept in constant agitation, with two objects — 
first, to remove air, and so obtain clear ice ; and second, to 
equalize the temperature throughout, so as to prevent the water 
freezing on the surface, as it ordinarily does on a pond. The 
ice is formed first round the sides of the cell, and gradually 
thickens till it closes up in the centre. The clearness of the 
ice is greatly increased by slow freezing, and to obtain this 
desirable condition the time allowed is from 60 to 90 hours. 
Each block of ice measures 3J feet broad by 4 feet long, and 
is 1 3 inches in thickness ; the weight varies from six to seven 
hundredweight. A simple contrivance to facilitate the removal 
of the ice by a crane travelling on rails laid on beams over- 
head, is a loop of rope which is frozen into each block. The 
ease with which, when placed on the ground, these large blocks 
can be slid about by the men is very advantageous. In order 
to loosen the ice from the cells, brine at any temperature above 
32° F. is made to circulate in place of the frigorific liquid, and 
so greatly are the metallic vessels cooled that it requires a period 
of about an hour to loosen one of the blocks. 
The magnitude of the operations is such that the engines 
can be worked up to 100-horse power, and are capable of turn- 
ing out 30 tons of ice per day. On the occasion of a recent 
visit to this interesting factory there were 180 tons of ice in 
store, and some of the blocks were five weeks old. We have an 
apparent paradox in the fact that the combustion of one ton of 
coal in the furnace fires will produce eight tons of ice. 
In the last number * of the Popular Science Eeview it was 
found necessary to refer to the researches of Faraday and others 
on the liquefaction of gases, and of Professor Andrews on the 
continuity of the liquid and gaseous states of matter ; it is 
therefore of great interest to note how a purely scientific fact 
* See i( Mineral Cavities and their Contents.” 
