Meteorological observations and essays / By John Dalton.

  • John Dalton
Date:
1834
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Licence: Public Domain Mark

Credit: Meteorological observations and essays / By John Dalton. Source: Wellcome Collection.

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    me of only a few yards in diameter. In time the sun pierced the fog, and became just visible ; for half an hour it was alternately brighter and darker, till at length the fog presented a smooth white sea on a level with the summit of the mountain, ex- tending all around to an indefinite distance, and was most brilliantly illuminated by the sun. The day continuing fine, this white sea gradually sunk into the valleys, and left the guide and me ona rock in the midst of an island situated in this ocean. Soon after, other mountain summits projected out of the ocean; and the views were wonderfully grand: at last the mist vanished from the valleys, leaving only one of them, which happened to be shaded by the mountain, with a level stratum of cloud as white as snow, at the bottom. The clouds thus dissolved left the atmosphere in the most trans- parent state I had seen it. Both sea and land views were uncommonly fine. Several ships were seen at sea, and the whole of the Isle of Man and part of the sea beyond it were full in view. In the above instance we see an example of the heat of the sun dissolving a cloud, or converting it into steam, beginning at the wpper surface of the cloud and proceeding downward. ‘There are other times when the heat operates on the under surface of the clouds first, and the solution proceeds up- ward. In this case the cloud appears to ascend, contrary to the law of gravitation ; the phenomenon is not unfrequent after a foggy morning in the summer. It is considered a prognostic of a fine DD