ICE IN INDIA. 171 



intelligent gentleman, David Scott, Esq., says the subject 

 of arliticial congelation is not so well understood by scien- 

 tific men in Europe as it might be. The old story of eviipo- 

 ration being at the bottom of the process, and porous pans 

 being necessary for its success, is repeated by one author 

 after another, although nothing can be more erroneous. In 

 respect to the first, it seems sufficient to observe, that when 

 ice is produced in temperatures above the freezing-point, a 

 plentiful deposition of dew is always going on, which seems 

 to be altogether inconsistent with the idea of air being in a 

 state capable of receiving -fresh accessions of moisture. Mr. 

 Scott found, by repeated experiments, that ice may be pro- 

 duced although a thin film of oil be spread over the surface 

 of the water, — the latter being contained in glazed plates, 

 which indeed answer much better than the porous pans of 

 the countr_y, the ice in them being invariably thicker, and 

 the water, when it does not actually freeze, somewhat colder 

 thun the similar contents of porous pans placed in exactly 

 the same situation. The fact is that the natives use porous 

 pans from necessity, there being no other description of 

 earthenware manufactured in the country ; but so well ar? 

 they aware that the ;;oro*iVy of the vessels is of no advanta^re, 

 that they usually rub them with grease for the purpose of 

 more easily taking out the ice, and also facihtating the pro- 

 cess, by keeping the straw upon which they are placed in a 

 perfectly dry and non-conducting state. Mr. Scott repeated 

 some of Dr. Well's experiments, and obtained interesting 

 results. On one occasion, a turban being suspended across 

 the pit three feet above the pans, it, as it always does, pre- 

 vented the formation of ice in those inunediately under it ; 

 and in several which it only partially covered, ice was formed 

 on the half of the water out of this perpendicular line, while 

 that under the turban was fluid. Two strings crossing each 

 other, and placed at a less height above a pan, will also 

 •livide the ice into four quarters ; but it is obvious that these 

 results will not always be obtained ; for, if the temperature 

 be rather lower than would be necessary to freeze the water, 

 j^upposing no impediment to exist, the whole may be frozen, 

 although partially covered ; and, on the other hand, if just 

 sufficient to freeze the water under the most favourable cir- 

 cumstances, the contents of a vessel not fully exposed to the 

 influence of the sky may remain fluid throughout. Mr. Scott 



