540 THE POPULAR SCIENCE MONTHLY. 



selves to one stone as a nucleus, and then the mass so formed has 

 received external coatings of ice. The compound structure of 

 such stones becomes manifested when the mass gradually thaws. 

 In some cases these stones are coated with crystals of ice in six- 

 sided prisms and pyramids, as perfectly formed as the specimens 

 of quartz or calc-spar crystals which are to be seen in mineral col- 

 lections. It is very hard to believe that such beautifully formed 

 crystals as these can be the product of any instantaneous process 

 of formation. 



It is these heavy blocks of ice which do the greatest amount 

 of damage, as naturally a lump, weighing even an ounce, is a 

 formidable missile when it falls from a height of even a thousand 

 feet. When these falls are about to take place, observers have 

 reported that a peculiar rattling sound is heard in the atmosphere, 

 evidently from collisions between these stones striking one an- 

 other in their fall. A very careful observer, who was overtaken 

 by one of these falls in the Caucasus, near Tiflis, states that it oc- 

 curred immediately after an ordinary hail-shower, and that he 

 could see the successive showers marching over the country, and 

 noticed that, between the last edge of the falling hail and the 

 front edge of the falling ice-blocks, there was a distinct break, 

 through which he could see the sun shining on the hills in the 

 background. It was on this particular occasion that the best 

 specimens of crystal-bespangled hailstones have been recorded and 

 sketched, but others have been reported from Natal, and quite 

 recently from Philadelphia, October 1, 1889. When such a visita- 

 tion of ice-lumps takes place, the entire crops of the district af- 

 fected by it are destroyed. Such a storm passed over Richmond 

 in August, 1879, and in five minutes some ten thousand pounds' 

 worth of damage was done, principally to conservatories. Natu- 

 rally, Kew Gardens were among the principal sufferers. 



It is a problem as yet unsolved to account for the suspension 

 in the atmosphere of such objects as these hailstones, which fre- 

 quently weigh much over an ounce. A recent theory, which 

 seems to carry some probability with it, supposes that in the 

 heart of every hail-cloud there is a whirlwind, or what is usually 

 but erroneously termed a " tornado." It is well known that such 

 disturbances exert a prodigious lifting power, raising heavy ob- 

 jects, such as carts, house-roofs, and even trees, and transporting 

 them to considerable distances. The theory is, that when a drop 

 of water in such a cloud is congealed it is carried round and 

 round in the vortex and lifted up, more moisture being condensed 

 and frozen upon it at each gyration, until at last it is thrown out 

 and falls. This would account for the alternate layers of which I 

 have already spoken, but will not account for the formation of 

 crystals, a growth which usually requires a considerable time. 



