of Dr. Holyoke. 113 
difference for the two years and four months, between the night 
thermometer and that at ten P. M., being 7,53°. Taking this as 
the basis of the. correction, it will still farther reduce the estimate 
of the true temperature, making that of the first seven years 
45,16°, and of the whole period, 46,620. 
After the year 1821, Dr. Holyoke discontinued keeping his 
meteorological journal in the same ample form. But, notwith- 
standing his advanced age, he did not altogether lay aside the 
habit of so many years. By the kindness of his grandson, the 
present E. A. Holyoke, M. D., of Salem, I am enabled to lay 
before the Academy the journal of two additional years, 1822 
and 1823, giving the extremes of heat and cold, and the state of 
the weather each day. The mean of the two years by these 
observations, is 46,23°; differing but little from the mean of the 
whole period, according to the proposed correction. 
There ought to be still another correction, however, applied 
to these results, if we are to regard them as a true expression of 
the temperature of the climate. No allowance is made for the 
effect of reflected heat. Although the thermometer hung con- 
stantly in the shade, the sun shone upon the buildings on the op- 
posite side of the street, and upon the pavement. For this 
reason the observation at noon probably indicates a temperature 
somewhat above the greatest daily heat of the atmosphere gen- 
erally. We have no data by which to estimate very accurately 
the amount of the error from this cause ; but it can hardly be less 
than from one to two degrees; which would reduce the mean 
temperature of Salem, from half a degree to a degree, lower than 
we have just made it from these observations, and fix it nearly 
at 45,5°. 
24 
