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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    appear to be two or more waves of temperature, or ascents and descents. Humso.pr has noticed the fact ; and he has referred to my explanation of the cause. (Memoirs, page 508.) The reference is to the part in italics at page 125 of my Essays, (first edition,) or at page 119 of the present edition. My own explanation given in that place, I have reason to think, is too brief to be generally intelli- gible, and I shall therefore unfold it a little here. It has been shown in the Essay on winds that air drawn from the polar regions towards the equator, by reason of its superior specific gravity, would go on the meridian, were it not for the diurnal rota- tion of the earth; but this rotation or motion of the earth’s surface, from West to East, causes the air relatively to move westward, so that, uniting the two motions of North or South with West, the real tract of the air over the surface of the earth is, in the northern hemisphere, towards the 8. and towards the W. or a N.E. current, and in the Southern hemisphere, towards the N. and W. ora S.E. current. These currents do not move over the surface of the earth in great circles nor less circles of the sphere, but in spiral lines, or directions somewhat like the oblique rhumb-lines, and always convex towards the East. What we have just de- scribed relates to the wnder currents of the atmo- sphere. The upper currents will be spiral lines, in diametrically opposite directions, or S. W. and N.W.. From this statement it will follow, that a strong S. W. wind blowing on the West coast of