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VII, —Inquiries about Terrestrial Temperature ; to which is added an Index to M. 
Dove's Five Memoirs on the Temperature of the Globe. By James D. Forzes, 
D.C.L., F.R.S., Sec. R.S. Ed., Professor of Natural Philosophy in the Univer- 
sity of Edinburgh. 
(Read 7th March 1859.) 
1. To find the numerical law according to which the temperature of a place 
varies with its latitude, is an empirical problem which has, since the middle of 
the last century, from time to time engaged attention. 
2. LAMBERT, Mayer, and Kirwan in the last century, Ds HumBotpt, Brewster, 
Kamrz, and Dove in the present, may be cited amongst those who have investi- 
gated formulze which express, with more or less accuracy, the mean temperature 
of a place in terms of its latitude. 
3. The formulze proposed are mostly reducible to two types—a variation de- 
pending upon the cosine of the latitude simply (that of Sir D. Brewsrsr), and 
one depending on the square of the same quantity (that of Mayer). 
4, There is no doubt a measure of truth in both these assumptions. If we 
select maritime stations in the northern hemisphere (and these, on the whole, 
furnish the most numerous class of observations), the simple cosine affords a re- 
markable approximation to the law of terrestrial temperature. If we take exclu- 
sively observations in the interior of continents, then the temperature decreases 
more nearly with the square of the cosine; and if we include both classes of 
stations indifferently, the approximation afforded by the latter law seems still to 
be the best. 
5. To De HumsBo.pt, Kamrz, and Dove, we are indebted for the most important 
accumulations of materials derived from observation for the elucidation of this 
subject. Ds Humsoupt, however, had the singular merit of giving an empirical 
generalization of the facts by means of his isothermal lines, which indicate, in a 
manner equally natural and instructive, the distributionof temperature over the 
globe, after correction for the elevation above the sea of the places of obser- 
vation. 
6. The same philosopher pointed out with great skill and acuteness the physical 
influences which prevent the isothermal lines from being everywhere parallel to 
the equator, such as the irregular distribution of land and water, and the influence 
of permanent or periodical currents in the ocean and the air. 
7. Thus, in his hands, this part of the science of meteorology passed out of the 
domain of barren mathematical generalization into that of rational physics. 
8. Sir Davip BrewstTER endeavoured later to show that there are two poles or 
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