Difference between revisions of ".Mzc2.NzQ5Ng"
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| − | on the higher ones. I shall add, that though my | + | |
| − | + | on the higher ones. I shall add, that though my hygrometer | |
| − | + | was exposed to the open air on the mountain, | |
| + | as it was in the plain, yet it was not so much | ||
insulated there, being tied to the box of my portable | insulated there, being tied to the box of my portable | ||
barometer The difference observed, however, is so | barometer The difference observed, however, is so | ||
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101. The observation of the 13th of September | 101. The observation of the 13th of September | ||
| − | seems likewise to throw some light upon the | + | seems likewise to throw some light upon the phaenomena |
| − | + | of dew. We know that when the sky is | |
cloudy, there is little or no dew, and it has likewise | cloudy, there is little or no dew, and it has likewise | ||
been observed from this very circumstance, that the | been observed from this very circumstance, that the | ||
air is not so much cooled after sun-set. The cause | air is not so much cooled after sun-set. The cause | ||
| − | of these differences appears to | + | of these differences appears to me to be, that when |
there are no clouds in the air at sun-set, or when | there are no clouds in the air at sun-set, or when | ||
they are dispersed the heat of the inferior air, and | they are dispersed the heat of the inferior air, and | ||
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again in dew; but when the clouds are continued, | again in dew; but when the clouds are continued, | ||
and thus separate the inferior from the superior air, | and thus separate the inferior from the superior air, | ||
| − | they prevent this dissipation of the heat, and the | + | they prevent this dissipation of the heat, and the vapours |
| − | + | remain suspended. And if the sky grows | |
cloudy some hours after the setting of the sun, and | cloudy some hours after the setting of the sun, and | ||
after the heat has sensibly diminished in the inferior | after the heat has sensibly diminished in the inferior | ||
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the inferior air. This appears in the observation I | the inferior air. This appears in the observation I | ||
am speaking of. The clouds having been sepa- | am speaking of. The clouds having been sepa- | ||
| − | H 2 rated | + | H 2 |
| + | |||
| + | [[catchword]] rated [[/catchword]] | ||
Latest revision as of 08:58, 20 October 2018
[ 51 ]
on the higher ones. I shall add, that though my hygrometer was exposed to the open air on the mountain, as it was in the plain, yet it was not so much insulated there, being tied to the box of my portable barometer The difference observed, however, is so considerable that, notwithstanding the concurrence of all these particular causes. I cannot bot ascribe it in some measure to that general one which I have suspected, namely, that there is comparatively a less degree of humidity in the upper than in the lower parts of the atmosphere.
101. The observation of the 13th of September seems likewise to throw some light upon the phaenomena of dew. We know that when the sky is cloudy, there is little or no dew, and it has likewise been observed from this very circumstance, that the air is not so much cooled after sun-set. The cause of these differences appears to me to be, that when there are no clouds in the air at sun-set, or when they are dispersed the heat of the inferior air, and that which rises from the earth, dissipates itself into the superior regions, and then the vapours which are dispersed throughout the air condense and all down again in dew; but when the clouds are continued, and thus separate the inferior from the superior air, they prevent this dissipation of the heat, and the vapours remain suspended. And if the sky grows cloudy some hours after the setting of the sun, and after the heat has sensibly diminished in the inferior air, it encreases again in it; because the heat, which continues to rise out of the earth, is accumulated in the inferior air. This appears in the observation I am speaking of. The clouds having been sepa- H 2
catchword rated /catchword
