In calm Weather, during Summer, the contrary Event happens: but more particularly in hot Climates. For the Country being hotter than the Town; a Depression of the Atmosphere takes Place, and scatters the Smoke on all Sides round the Town.
The Cities in Italy, and other hot Climates, on Account of the Buildings, and desirable Narrowness of the Streets, form one contiguous Shelter, Arbor, or grand Parasol: For which Reason, the Nobility leave the Country, and reside in the Towns during Summer: there finding a Coolness and Refreshment unknown on the scorching Plains.
A Reception and Dispersion of Air takes Place; as will presently be mentioned.
The same ocular Proof and Process in the Evaporation of Steam, accounts at once, for a curious Phenomenon constantly observable on all Waters; viz. a narrow smooth irregular Surface of considerable Length, nearly in the Direction of the Wind, yet unaffected by it: all which is probably nothing more than rising Volumes of elastic invisible Steam; resisting the two nearest descending Waves of air; and preventing them from approaching the Surface of Water, over which the Steam is compressed; and there producing a temporary calm.
[67]Phil. Trans. for 1777, Page 470. Thibet in Lat. 31, cold with Snow and Frost.
See Ullòa’s Voyage to South-America, Book 6, Chapter 7; where he describes the snowy Mountains, under the Equator.
As the Weather, near the Equinoctial, is more regular, its Changes closely following those of the Moon; and also the Winds and Hurricanes more violent; the Truth of the foregoing Theory will receive the strongest Confirmation by tracing the Effects of depressing torrents of air, in the Island of Jamaica, extracted from the Author already mentioned.
“The cool Vapour rushes from the Mountains towards the hot dry Air, which hovers over the Savannahs or Vallies.
The Rain falls heaviest in the Mountains. Vol. 3, Page 600.
The Land-Wind after Rain, proceeds from that Quarter whence the Rain has fallen heaviest; and seems to rush from above.