ARISING FROM DIFFERENCE OF LATITUDE. 
15 
On looking over the table, we can hardly fail to notice the slower rate of decrease in 
temperature as we rise from the valley of the Mohawk, than in other parts of the State; 
occasioned probably by the greater prevalence of northwest winds in that valley, which 
tend to reduce its temperature. In the former it averages but 1° in 581 feet; while in 
the latter, it is 1° in 304 feet. The mean of all the observations compared gives 1° for 
every 372 feet; but making some allowance for the slow rate in the valley of the Mo¬ 
hawk, I shall assume it at 1° in 350 feet. This result does not differ materially from 
that which was obtained from observations taken in balloons and on mountain heights, 
though it would seem from philosophical considerations that there should be a difference. 
In regard to the influence of difference of latitude on temperature, we know that the 
mean annual temperature is greatest near the equator and least toward the poles. If we 
regard the difference between the .equatorial and polar temperatures as the amount due to 
the sun’s influence, Mr. Kirwan found that in mid-ocean this is always nearly proportional 
to the square of the cosine of the latitude of the place; and in accordance with this law, 
he calculated a table showing the temperature due to all latitudes. In latitudes varying 
from 30° to 50°, he makes the temperature diminish about T \ of a degree for each degree 
of latitude. This, it must be recollected, is intended as the rule on the ocean, remote 
from either continent. Observations show that such an allowance is too small in Europe, 
and much more so in this country, where a given change of latitude affects the climate 
more than it does there. 
To find the law in this country, particularly in our own latitude, I compared the tempe¬ 
rature of places along the Hudson river, together with Cambridge and Plattsburgh. I 
selected these places, because, with the exception of difference of latitude, the general 
circumstances which affect the climate are very similar in them all. They all lie in val¬ 
leys extending in a north and south direction; are all nearly on the same level, except 
Cambridge ; and the character of the winds is very similar in them all.* The observations 
at all these places were taken between the years 1826 and 1842, but not all during the 
same years. It was therefore necessary, in order to compare them properly, to seek for 
some place where they had been taken during the whole period without interruption, that 
I might know whether the mean temperature of the years observed at any particular place 
was higher or lower than the general average. I selected the observations at Albany as 
such a standard of reference. Its central position in regard to the other places, as well as 
the care with which the observations there are known to have been taken, seemed a valid 
reason for doing so. 
I next proceeded to compare the mean temperature of each of the places selected, with 
that of Albany during the same years, and the latter with its mean temperature for the 
whole seventeen years, varying that of the place compared by the same amount. I then 
reduced the temperature of all to the level of the sea, by allowing 1° for every 350 feet of 
See article on the winds of the State, published in the Regents’ Report for 1840. 
