382 Mr. Hera path on True Temperature, and the [Nov. 



whose pipe was in a drier and more elevated region, assured me 

 be never perceived the least tendency to dampness, much less 

 did he experience any inconvenience from such a thing. A 

 simple desiccative substance put near the mouth of the tube in 

 the former instance, and frequently renewed, would probably 

 obviate the dampness complained of. However, under all cir- 

 cumstances, the constant renewal of air which fire occasions 

 appears to me much more conducive to health, if it were only 

 for dissipating and carrying off the incessant exhalations of the 

 body, than this new method. To be convinced of the utility of 

 tire in changing the air, one need only enter a room from the 

 fresh air where there is a fire and company, and afterwards 

 where there is an equal company and no fire, and he will not 

 want to be told which is the more healthy apartment. 



Cor. 5. — The ready intermixture of gases one with another, 

 and of aqueous vapour with the atmosphere, has long been a 

 problem of considerable difficulty with philosophers. To account 

 for phenomena of this nature, they have created a kind of attractive 

 affinity between the parts of different bodies, and yet with this 

 assistance they find it no easy matter to give to their views even 

 the semblance of probability. Our theory accounts for such 

 phenomena from the nature of the bodies, and, therefore, 

 explains the mixture and ascent of aqueous vapour in the atmo- 

 sphere from the principles of constitution. In every evaporation, 

 however, the evaporated particles, by striking in all directions 

 aoainst the particles of the atmosphere, must necessarily occa- 

 sion reflections of many of the vaporous particles to the surface 

 of the fluid. Of these reflected particles some of them must 

 evidently be recondensed on the fluid ; and as the chance of 

 striking with their condensible sides is in proportion to the 

 quantity reflected, and the quantity reflected to the quantity 

 evaporated, the quantity recondensed will be in proportion to the 

 quantity evaporated. Therefore these recondensations will not 

 any ways affect the truth of the propositions I have advanced. 



If evaporation takes place in a still atmosphere, the reconden- 

 sation will proceed without interruption ; but if a current of air 

 passes over the surface of the evaporating body, the vapour as 

 it is raised will be in part carried off, and the recondensation on 

 a limited surface diminished. The greater the current the 

 crreater will be the effect, and the less the amount of recondensa- 

 tion. In moderate winds, the diminution of the recondensation 

 -will be accurately proportional to the current, if the evaporating 

 surface has a sensible extent ; but when the velocity of the cur- 

 rent is very great, or its ratio to the linear extent of the evapora- 

 ting surface exceeds a certain quantity, I find the decrement of 

 recondensation follows a different law. Of these things, how- 

 evei - , I may treat more fully hereafter, when I shall be better 

 provided with experiments to verify the laws I shall develop. 



Because in moderate currents, that is, in all such as we 



