12 
VARIATION OF TEMPERATURE 
The mean temperature of these places for seventeen years (so far as reported) ending 
with 1842, was 46°.49; but the relative temperature of different sections of the State, 
while it depends chiefly on the latitude* and elevation, is modified in some degree also by 
a variety of other circumstances, such as the situation in regard to the sea, or other large 
bodies of water, both as it respects proximity and direction; the configuration of the sur¬ 
face, whether level or hilly, and the position and slope of the hills; the nature of the 
soil, and the extent of cultivation in the surrounding country. And before proceeding 
farther, it becomes necessary to investigate briefly the laws by which we shall be guided in 
relation to the three main circumstances mentioned above ; so that having made a proper 
allowance for these, we may see more clearly the effect of the others. 
That the temperature of the air diminishes as we ascend, is a fact familiar to every one ; 
but the rate of decrease, especially where the slope of the country is gradual, is by no 
means so well ascertained. The experiment was tried at Paris by Gay-Lussac, who rose 
in a balloon to the height of nearly 23,000 feet, and found the difference in temperature 
to amount to 1° for every 316 feet of ascent. The mean of two other similar experiments, 
tried one at the same place and the other at Rodez in the southern part of France, each 
at a height of a little less than 12,000 feet, showed a decrease in temperature of 1° in 400 
feet. Mr. C. F. Durant has kindly furnished me with quite a number of observations of 
the same kind, taken by him in seven different ascensions in a balloon, from New-York, 
Albany, Baltimore and Boston, in the years 1831, 3 and 4. The height at which they 
were taken varied from 1500 to 8000 feet. Taking twenty of his observations, which are 
capable of being arranged for comparison in twelve pairs, I find the decrease of tempera¬ 
ture to be 1° in 425 feet. If, however, we reject the comparison of two pairs of observa¬ 
tions, which show great discrepancies from the rest, and which appear by the circumstances 
in which they were taken to be entitled to less confidence, the result is 1° to every 370 
feet of elevation. 
From numerous observations made by Humboldt among the Andes and Cordilleras, he 
deduced the rate to be as follows, viz: For the first 1000 French metres = 3281 feet, 1° 
for every 319 feet; for the second, 1° in 538 feet; for the third, 1° in 443 feet; for the 
fourth, 1° in 250 feet; for the fifth, 1° in 331 feet; and for the whole on an average, 1° 
in 351 feet. In a single observation taken on Chimborazo at the height of about 19,300 
feet, the difference in temperature was 1° in 399 feet. The mean of six pairs of simulta¬ 
neous observations on the Alps and the plains below, showed a diminution of 1° in 262 
feet; one on the Peak of Teneriffe and at Orotava below, showed 1° in 412 feet; one 
on Mount Etna and at Catania, 1° in 312 feet; the mean of twenty-one on the Pyrenees 
and at places below, 1° in 305 feet; the mean of seven taken at Clermont in France and 
on elevations in its vicinity, 1° in 267 feet. Twenty-eight simultaneous observations have 
* Several recent writers reject latitude as one of the elements of temperature, but, as it seems to me, unphilo- 
aophically. 
