1833.] Means of making Ice by the Natives of Bengal. 81 
under the level of the ground. Numerous beds of this kind are formed, 
with a narrow path between them, in which large earthen water-jars are 
sunk into the ground for the purpose of having water near, to fill the 
shallow unglazed earthen vessels in which it is to be frozen. These 
dishes are nine inches in diameter at the top, diminishing to 4,5 inches 
at the bottom, 1,3, deep, and 5 of an inch in thickness; and are so 
porous as to become moist throughout when water is put into them. 
During the day, the loose straw in the beds above the sheaves is oc- 
casionally turned up, so that the whole may be kept dry, and the water- 
jars between the beds are filled with soft pure water from the neigh- 
bouring pools. Towards evening, the shallow earthen dishes are ar- 
ranged in rows upon the straw, and, by means of small earthen pots tied 
to the extremities of long rods of bamboo, each is filled about a third 
with water. ‘The quantity, however, varies according to the ice ex- 
pected; which is known by the clearness of the sky and steadiness with 
which the wind blows from the N. N. W. When favourable, about 
eight ounces of water is put into each dish, and when less is expected, 
from two to four ounces is the usual quantity; but, in all cases, more 
water is put into the dishes nearest the western end of the beds, as the 
sun first falls on that part, and the ice is easier removed from its solu- 
tion being quicker. There are about 4590 plates in each of the beds 
lately made, and if we allow five ounces for each dish, which presents a 
surface of about four inches square, there will be an aggregate of 239 
gallons, and a surface of 1530 square feet of water in each bed. 
In the cold season, when the temperature of the air at the ice-fields is 
under 50°*, and there are gentle airs from the northern and western direc- 
tion, ice forms in the course of the night in each of the shallow dishes. 
Persons are stationed to observe when a small film appears upon the 
water in the dishes, when the contents of several are mixed together and 
thrown over the other dishes. This operation increases the congealing 
process. A state of calmness has been discovered by the natives to 
diminish the quantity of ice produced; and this is confirmed by the fact 
well known in our laboratories, that water may be gradually cooled down 
many degrees below the freezing point without congealing, provided 
it be kept perfectly still. When the sky is quite clear, with gentle 
steady airs from the N. N. W. the freezing commences before or about 
midnight, and continues to advance until morning, when the thickest 
ice isformed. I have seen it 5th of an inch in thickness, and in a few 
very favourable nights, the whole of the water is sometimes frozen ; 
* Fahrenheit’s thermometer is used in the following essay : a minute having 
been allowed for each experiment. 
M 
