Dr. A. Waller's Microscopic Observations on Hail. Ill 



nature we not unfrequently meet with experiments performed 

 for us, which if examined with care would, I believe, furnish 

 us with the desired information. 



In the winter months, during a hoar frost, we sometimes 

 find, adhering to minute filaments on the hedges, such as those 

 of the spider's web, very minute globules of transparent ice, 

 such as exist in hail and sleet. On other occasions, instead 

 of globular forms, we find others of crystalline shapes. Care- 

 ful observations made as they are in process of formation, with 

 the instruments we possess for examining the state of tempe- 

 rature and the movements of the atmosphere, would no doubt 

 give us the formula of these two deposits. The same obser- 

 vations would likewise enable us to determine, whether the 

 temperature of the air around is such that any existing mist 

 or fog must contain its globules in a solid state, according to 

 the hypothesis advanced by Descartes. I am inclined to be- 

 lieve that such is not unfrequently the case. 



It is evident that these globules, with the exception of their 

 being formed on the surface of bodies which are stationary, 

 are in all respects exactly similar to the particles of sleet. 

 Frost, which forms in the same way, presents under the mi- 

 croscope crystalline forms, which are so much like those of 

 snow that I have scarcely been able to distinguish one from 

 the other. But if such deposits formed on the surface of the 

 earth present analogies so great to those formed in the atmo- 

 sphere, that they almost deserve the names of "ground sleet" 

 and " ground snow," it naturally suggests that something like 

 hail may also occasionally be produced in the same way, or 

 in other words, the globules of ice may be found in a state of 

 agglomeration. I have seen somewhere a definition of hoar 

 frost, which describes it as a collection of spherules of ice; 

 and according to the view I take, I believe that such is some- 

 times the case, although the observations I have hitherto 

 made, I must confess, have not yet enabled me to detect this 

 structure in hoar frost*. 



Kensington, June 1846. 



* Since making the foregoing observations, I have had an opportunity 

 of witnessing another storm, which occurred on June 23, 1846, when a 

 violent shower of rain fell, and having continued for about a quarter of an 

 hour, it became mixed with hail, which had been preceded for a few mi. 

 nutes by thunder. The largest hailstones attained the size of a French 

 bean, and were accompanied by others of all sizes down to that of a pea. 

 Their shape was generally biconical ; colour, a dull, without any external 

 envelope of transparent ice, resembling in all respects those I had previ- 

 ously examined on other occasions, with the exception of one, which was 



