of the Lower Strata of the Atmosphere. 43 
height of 105 feet it was at—7°.4, giving a total difference of 
8° 8 for an elevation of 105 feet. 
On the morning of the 21st January, still colder than the 
preceding, at six o’clock the thermometer, at 2 feet above the 
ground, was at—21°.2; at the height of 52 feet it was at 
—15°.5 ; and at 105 feet, at—13°.7. The increase of tempera- 
ture, it is thus seen, is less considerable than on the preceding 
day ; which is no doubt owing to this, that the cold of the 
earth’s surface had had time to extend itself to the somewhat 
more elevated strata of the atmosphere. It amounts, never- 
theless, to 5°.7 for a height of 50 feet, and to 7°.5 for a height 
of 100 feet; a difference which exceeds by many degrees the 
maximum of that which has been observed during the warm 
season. A mean of twelve observations made both at sunrise 
and sunset, during perfectly serene weather, and the ground 
being covered with snow, afforded a difference of 5°.4 between 
the temperature of the air at the height of 2 feet and that at 
52 feet above the ground. By comparing the station at 2 
feet with that at 105, this difference was 6°.4. 
In winter, when the ground was not covered with snow, the 
difference between the temperature of the lower strata of the 
atmosphere appeared to me to be less considerable ; it always, 
however, exceeded the maximum of what was observed during 
the serene evenings of summer and autumn. The maximum 
of difference observed by me when the ground was not cover- 
ed with snow, occurred on the Ist of December. The ther- 
mometer, 2 feet above the ground, marked—4°.7 ; at 52 feet 
+ 0.9; and at 105 feet, + 1.4; thus giving a difference of 
5°.6 between two beds of air separated by an interval of 50 
feet, and of 6°.1 for an interval of 100 feet. The mean in- 
crease of temperature, calculated from a series of twenty ob- 
servations, made partly in December and partly in February, 
was found to be 3°.30 for a difference of elevation of 50 feet, 
and 3°.45 for a difference of 100 feet. We thus see that, in 
the circumstances above mentioned, the increase of tempera- 
ture as we ascend, even during perfectly serene weather, is 
extremely slight, reckoning on a height of 50 feet ; and we 
are of opinion that we are not far from the truth by fixing the 
extreme limit of this increase in winter below 100 feet, how- 
