In the system of Eastern America, the mean annual temperature from the coast
of Labrador to Boston changes 1.6??degrees for every degree of latitude;
from Boston to Charleston about 1.7 degrees; from Charleston to the tropic
of Cancer, in Cuba, the variation is less rapid, being only 1.2 degrees. In
the tropics this diminution is so much greater, that from the Havana to
Cumana the variation is less than 0.4 degrees for every degree of latitude.
The case is quite different in the isothermal system of Central Europe.
Between the parallels of 38 degrees and 71 degrees I found that the decrease
of temperature was very regularly 0.9degrees for every degree of latitude.
But as, on the other hand, in Central Europe the decrease of heat is 1.8
degrees for about every 534 feet of vertical elevation, it follows that a
difference of elevation of about 267 feet corresponds to the difference of
one degree of latitude. The same mean annual temperature as that occurring
at the Convent of St. Bernard, at an elevation of 8173 feet, in lat. 45
degrees 50' should therefore be met with at the level of the sea in lat. 75
degrees 50'.
In that part of the Cordilleras which falls within the tropics, the
observations I made at various heights, at an elevation of upward of 19,000
feet, gave a decrease of 1 degree for every 341 feet; and my friend
Boussingault found, thirty years afterward, as a mean result, 319 feet.
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