73 
together with some remarks upon sensible cold . 
The circumstances that particularly engaged my attention 
were wind, and moisture. With these views the following 
experiments were made, and verified by repeated trials. 
Experiment i. 
1 82 1, January 3. A strong east wind. 
The temperature of the air 31 0 . 
The thermometer in this, and all the 
experiments, being previously raised 
to ioo°, in the manner before-men- 
tioned, the descent of the mercury 
from that point was observed as fol- 
lows : 
After 10" it was 78®. Decrement 22° 
20" 6o° 1 8° 
30" — 52° 8° 
By the decrements, it is to be under- 
stood the descent in each successive 
ten seconds. This is added, because I 
consider it as the proper measure of 
the sensible cold , so long as the ther- 
mometer retains a heat approaching to 
that of the human body. 
Experiment 2. 
1821, Jan. 4. No perceptible wind. 
The temperature of the air 30°, the 
atmosphere hazy. 
After 10" therm. 89° Decrement ii° 
20" 8o° • — t 9 0 
30" 71° 9 0 
Experiment 3. 
1821, Feb. 10. A strong east wind. 
Temperature of air 47 0 . The atmo- 
sphere clear, with sunshine. 
After 10" therm. 82° Decrement 18 0 
Experiment 4. 
1824, Jan. 9. A cold fog. No wind. 
Temperature of the air 37 0 . 
After 10" therm. 92 0 Decrement 8 C 
20" 85° — — — 7 0 
30" 79 0 6° 
The most superficial view of these experiments shows the 
prodigious effect of wind to increase the rate of cooling , which, 
I apprehend, constitutes sensible cold ; so that in experiment 3, 
though the thermometer suspended in the open air was 1 7 0 
higher than in experiment 2, yet the sensible cold was very 
considerably greater ; but when there was no wind, even a 
wet fog did not much, if at all, increase it. This, which at 
first sight may appear contradictory to experience is not, I 
believe, really so ; for though the power of such air to carry 
off the heat, of the body be indeed increased, yet so long as 
we remain at rest, we are in great measure unaffected by it ; 
MDCCCXXVI. 
L 
