Meteorological observations and essays / By John Dalton.

  • John Dalton
Date:
1834
Catalogue details

Licence: Public Domain Mark

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

    224/280 (page 198)
    whole of the rainy region of the atmosphere be- comes, especially during the fall of a thunder storm, nearly one continued cloud. Soon after the rain ceases, the strata of clouds either disappear, or be- come one stratum, or two or more strata, disposed probably at nearly equal intervals of distance. On the 7th of July, 1833, I had a remarkable illustra- tion of three strata of clouds, all moving in the same current of air. Being in Wythburn, at the foot of Helvellyn, in Cumberland, I observed the upper part of the mountain covered all the morning with clouds extending about one-third part down. The wind was moderate, and blowing across the valley, or at right angles to the extensive mountain range, and the morning was fine and gleamy: the passing cloud was slowly detached from the moun- tain side, and commenced its motion across the valley ; but it became gradually attenuated as it proceeded, and never reached further than the middle of the valley before it vanished ; so that for some hours this low stratum never made any pro- gress towards the west, further than to the middle of the valley. The west side of the valley, all this time, was quite clear, or more properly free from this stratum. There was a second and higher stratum above this, however, which was moving in the same direction, but much higher. From the less apparent velocity, I judged it to move in the same current as the lower stratum, but about twice the height ; it continued its course over the sum- mits of the opposite mountains uninterruptedly.