Page:Popular Science Monthly Volume 1.djvu/688

672 The mean for January, February, and March, for fifty-six years, is 35.56 degrees. The mean for the above selection is 35.23 degrees.

From this, it would seem that the mean temperature of the first three months of the year at Philadelphia is 2.66 degrees above that of New York, and that the same conclusion arrived at in the preceding instances reappears in this, viz., that there has been no change in the winter climate.

The Boston records reach back to 1780. Taking the same periods as in the preceding instances, as far as these records will permit, they are—first, 1797 to 1803; second, 1821 to 1827; third, 1831 to 1837; fourth, 1850 to 1856. It is to be remarked that these observations are not all from the same station.

The mean for January, February, and March, for eighty-six years, is 29.63 degrees. The mean for the above selection is 29.66 degrees.

The mean temperature for the first three months of the year at Boston is 3.27 degrees lower than that of New York. These records give no substantial reason for supposing that, during the period of time to which they refer, there has been any sensible change in the winter climate of that locality.

In like manner, making a selection from the Charleston records, first, from 1749 to 1755; second, from 1754 to 1760; third, from 1822 to 1829; fourth, from 1830 to 1836; fifth, from 1849 to 1855—which date from 1738.

In this series, again, unfortunately the observations are from different stations. They exhibit greater divergences than any of the preceding cases; but notwithstanding that, so far from invalidating,