An essay on dew and several appearances connected with it / By William Charles Wells.

  • William Charles Wells
Date:
1814
Catalogue details

Licence: Public Domain Mark

Credit: An essay on dew and several appearances connected with it / By William Charles Wells. Source: Wellcome Collection.

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    are certain preventives of its formation; and that, although ice is thus very readily procured by art in Bengal, during the winter, it scarcely ever occurs there naturally. The process described by Mr. Williams must, from its extent, 300 persons being employed in it, have been carried on for profit, and would, consequently, be conducted in the most economical manner. No excavations were made in the earth. A piece of ground, nearly level, containing about 4 acres, was divided into square plats, from 4 to 5 feet wide, which were surrounded by little mounds of earth, 4 inches high. In these inclo¬ sures, previously filled with dry straw, or sugar¬ cane haum, w^ere placed as many broad, shallow', unglazed, earthen pans, containing unboiled pump water, as they could hold. The air was generally very still, when much ice was formed; wind prevented its formation altogether. In the morning between 5 and 6h. at which time alone, Mr. Williams made his observations, a thermometer, with its bulb naked, placed on the straw, amidst the freezing vessels, was never found by him lower than 35°; and he has observed ice, when a thermometer so placed was 42°. Another thermometer, suspended 5| feet above the ground, was commonly 4° higher than that among the pans. It is possible, therefore, that Mr. Williams may have seen ice, a little before sunrise, when
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