of Dr. Holyoke. 115 
than twelve hours, commonly not so long.” And the opinion is 
extensively adopted, that in some way the severity of our climate 
has been materially mitigated since the days of our fathers. It 
remains to be seen how far this opinion is supported by this 
journal. 
From the fact already mentioned that the mean temperature 
of the whole period of thirty-six years is more than one degree 
higher than that of the first seven years, it would at first view 
seem that there is some indication of a progressive change. But 
when we examine the journal more in detail, the evidence of the 
change disappears. Of the five periods, of seven years, (the last 
period, however, containing only five years,) of which the results 
are published in the fourth volume of the Academy’s Memoirs, the 
mean of the fifth is the lowest, then the first, the fourth, and the 
second ; the third, from 1800 to 1806 being the highest. If we 
divide the whole into seven periods of five years, the two lowest 
are the first and the sixth; and the difference between the two 
periods is only two hundredths of a degree. The mean of the 
first ten years is 48,77°; that of the last ten years 47,85°, nearly 
a degree lower. The three highest successive years are 1793 
—1795, the three lowest in succession 1812-1814; the mean 
of the former being 50,69°, that of the latter 46,88°. The highest 
year in the whole series is 1793; the lowest, 1812, nineteen 
years later. 
It thus appears that this journal does not support the opinion 
that there has been a progressive increase of the temperature of 
our climate, in regard to the whole year. If we compare the 
spring months of the different years, we find the results nearly 
the same, both in respect to the whole spring, and to the 
months of March and April; thus showing that the opinion is 
