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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    unhurt through the winter. Again ; as things are, while low vegetable productions are prevented, by their covering of snow, from becoming colder than the atmosphere in consequence of their own radiation, the parts of trees and tall plants, which rise above the snow, are little affected by cold from this cause. For their extreme parts, now that they are destitute of leaves, are much smaller than the thermometers suspended by me in the air, which in this situation very seldom became more than 2° colder than the atmosphere. The larger branches too, which, if fully exposed to the skjr, would become colder than the extreme parts, are, in a great degree, sheltered by them; and, in the last place, the trunks are sheltered both by the smaller and the larger parts, not to mention that the trunks must derive heat, by con¬ duction through the roots, from the earth kept warm by the snow. In a similar way is partly to be explained the manner, in which a layer of earth or straw pre¬ serves vegetable matters in our own fields, from the injurious effects of cold ; since such a covering must prevent them, during still and serene nights, from radiating their heat to the heavens. V. The bare mention of the subject of this article will be apt to excite ridicule, it being an attempt to show, in what way the exposure of animal substances to the moon’s light promotes
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