Rain. 341 



of its latent caloric, though not affecting the transparency of 

 the air, so that " a shallow stratum of the lower and compara- 

 tively clear atmosphere " may " supply as much rain as a 

 densely- clouded and much deeper stratum in the higher 

 regions." Baxendell mentions also the interesting fact, that 

 the drops of water which drip from the upper part of the 

 shaft increase to an extraordinary size in the descent to the 

 bottom. 



It appears to me that the well-known phenomenon of rain 

 falling from a clear sky — a rain termed by the French serein — 

 has a suggestive bearing on the peculiarity we have been 

 considering. It proves that water may exist, even in drops, in 

 the atmosphere, without appreciably affecting its transparency. 

 And though it may be an uncommon thing for rain to fall 

 without appearing first in the upper regions of air — in the form 

 of cloud, yet it by no means follows that during a shower 

 rain might not be falling from the lower as well as from the 

 upper air-strata, without the transparency of the lower strata 

 being much or at all affected. I have noticed, always, that if 

 the eye be directed steadily at the drops of heavily-falling 

 rain, there will be seen flitting, as it were, among them minute 

 specks, which are seen on a closer observation to be small 

 particles of water. Now, it does not appear to me likely that 

 these, or most of them, are produced by the collision of the 

 falling drops— for the paths of two neighbouring drops must 

 be parallel, since the drops are subjected to precisely the same 

 set of influences. 



I believe the phenomenon to be one worthy of more careful 

 notice than it has received — in fact, I am not aware that it has 

 been noticed at all. The motions of the particles are them- 

 selves interesting — seeming almost as independent of gravita- 

 tion, wind- currents, or the like, as the motion of a flight of 

 insects would be. It is hardly necessary to observe that if 

 these particles show that rain is being generated in the lower 

 as well as the upper strata of the air, ail difficulty in explaining 

 the results of Professor Phillips's observations, vanishes at 

 once. 



