Dr. A. Waller's Microscopic Observations o?i Hail. 107 



April 6, 5 p.m. — A heavy fall of rain with hailstones about 

 the size of a sweet pea. Under the microscope, the hailstones, 

 when sufficiently thin, appeared to consist of spherical globules 

 of various sizes, as in fig. 1, mixed with others of an angular 

 outline. Air- bubbles as usual. 



The foreign matter was found to consist of particles like 

 sand, and others resembling microscopic lichens. 



May 10, 3 p.m. — Wind N.W. an hour or two previous, 

 bringing numerous masses of clouds, detached portions of 

 which rapidly disappeared under the action of the sun's rays. 

 Temperature warm; shortly before the fall of hail, the wind 

 blew violently in the most opposite directions. A few hail- 

 stones fell of nearly a globular form. Under the microscope 

 they gave off air-bubbles as usual, and all contained minute 

 amorphous particles, some of an organic appearance, as in 

 fig. 2. The thin disc of ice, besides the globular particles, 

 presented many minute circular spots of different sizes, which 

 as the ice melted, appeared to form the air-bubbles. These 

 presented a different appearance from the globular particles 

 before mentioned ; they were much less defined and more ir- 

 regular in their size. In some instances I could detect what 

 appeared to be globular particles imbedded in a matrix of ice. 



Air contained within Hailstones. 



It is remarkable that, in all the accounts of hailstones which 

 I have met with, I have not found any mention of the quantity 

 of air which is contained in their interior. Under the micro- 

 scope, the rapid formation of air-bubbles is the first point 

 which attracts the attention, giving rise to the idea that a che- 

 mical action disengaging a gaseous body must be taking place. 

 As I have invariably observed this in all the numerous hail- 

 stones which I have examined, I regard it as intimately con- 

 nected with all those which, like those I have met with, are 

 composed of separate globules, and have a semi-transparent 

 aspect. Although the greater part of this air is disengaged 

 during the process of liquefaction, some part of it remains in 

 the state of small air-bubbles, on the surface of the drop of 

 water resulting from the fusion of the ice, and may be per- 

 fectly distinguished by the unassisted eye. Hitherto I have 

 not been able to determine the amount of air which a hail- 

 stone is capable of containing, but as far as I have been able 

 to judge, it is more than the volume of the hailstone itself. 

 We must furthermore bear in mind, that as the density of the 

 atmosphere is less as we ascend, the original volume of the 

 air, supposing it to have been confined at the moment the hail 

 was formed, must have been much more considerable than at 



