1826.] Philosophical Transactions for 1826, Paris L and II, 137 



" The circumstances that particularly engaged my attention 

 were wind, and moisture. With these views the following ex- 

 periments were made, and verified by repeated trials. 



" Exp. I. — 1821, January 3. A strong east wind. The tem- 

 perature of the air 31°. 



" The thermometer in this, and all the experiments, being pre- 

 viously raised to 100°, in the manner before-mentioned, the 

 descent of the mercury from that point was observed as 

 follows : 



After 10'^ it was 78° Decrement 22° 



20'^ 60° 18° 



30'' 52° 8° 



*^ By the decrements, it is to be understood 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. 



*^ Exp. 2. — 1821, January 4. No perceptible wind. The 

 temperature of the air 30°, the atmosphere hazy. 



After 10'' therm. 89° Decrement 11° 



20" 80° 9° 



30'' 71° 9° 



*' Exp. 3. — 1821, February 10. A strong east wind. Tem- 

 perature of air 47°. The atmosphere clear, with sunshine. 



After 10" therm. 82° Decrement 18° 



20" 73° 9° 



30" ■ 64° — 9° 



*' Exp. 4. — 1824, Jan. 9. A cold fog. No wind. Tempera- 

 ture of the air 37°. 



After 10" therm. 92° Decrement 8° 



20" 85° 7° 



30" 79° 6° 



" The most superficial view of these experiments shows the 

 prodigious eftect of wind to increase the rate of cooling, which, 

 1 apprehend, constitutes sensible cold; so that in experiment 3, 

 though the thermometer suspended in the open air was 17° 

 higher than in experiment 2, yet the sensible cold- was very con- 

 siderably 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, 1 believe, really 

 so ; for though the power of such air to carry ofi:' the heat of 

 the body be indeed increased, yet so long as we remain at rest, 

 we are in great measure unaffected by it; so m-uch the effect of 

 wind exceeds that of mere moisture. It is by walking, or 

 riding, in such a state of the atmosphere, that we produce on 



