Meteorological observations and essays / By John Dalton.

  • Dalton, John, 1766-1844.
Date:
1834
Catalogue details

Licence: Public Domain Mark

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

    111/280 (page 85)
    and doubtless in the southern also, the winds are more tempestuous in winter than in summer.—See page 48. Now in order to perceive the reason of these facts, it must be remembered, that the heat is at all times greatest in the torrid zone, and decreases in proceeding northward, or southward ; also, that the poles may be considered as the centres of cold at all times: hence it follows, that, abstracting from accidental circumstances, there must be a constant ascent of air over the torrid zone, as has been observed, which afterwards falls northward and southward ; whilst the colder air below is de- termined by a continual impulse towards the equa- tor. And, in general, wherever the heat is greatest, there the air will ascend, and a supply of colder air will be received from the neighbouring parts.— These, then, are the effects of the inequality of heat. The effects of the earth’s rotation are as follow: the air over any part of the earth’s surface, when apparently at rest or calm, will have the same ro- tatory velocity as that part, or its velocity will be as the co-sine of the latitude ; but if a quantity of air in the northern hemisphere, receive an impulse in the direction of the meridian, either northward or southward, its rotatory velocity will be greater in the former case, and less in the latter, than that of the air into which it moves; consequently, if it move northward, it will have a greater velocity eastward than the air, or surface of the earth over which it moves, and will therefore become a SW. wind, or