Sciences of Meteorology and Terrestrial Magnetism. 175 



J. J. Waterston, bearing on the same subject, will be found in the 

 Fhilosophical Magazine for March, 1858. 



Clotjd8 aot) Rain. 



(IR.) To this department of our subject some important additions 

 have been made of late years. Meteorologists have long been divided 

 in their views regarding the internal constitution of clouds, and the 

 nature of fogs and vapour. These are all of the same integrant struc- 

 ture — that is, they consist of minute spherules, suspended at greater or 

 less heights in the air. We call them fogs or mist, when resting on the 

 surface of the earth ; when raised aloft, and viewed en masse, we name 

 them clouds. It is obvious, however, that there are differences in the 

 state of aggregation, or the degree of closeness among the particles ; and 

 these different states of density may develop pecuhar forces among the 

 component molecules. Now, some hold that the spherules are hollow, 

 and that the water serves only as an envelope, as in the case of a soap- 

 bubble ; others maintain that they are without internal cavity, and 

 resemble globules of quicksilver. Kaemtz inclines to the former view 

 {^Meteorology Translated, by Walker, p. 109, 1845). In his first report 

 to the British Association (Vol. I. of Reports, 18B3), Prof. J. D. Forbes 

 does not directly consider this branch of the subject. In his second 

 report {Report of Tenth Meeting, 1840), he merely alludes to it in a 

 short paragraph, and seems to incline to the view that the component 

 particles are vesicular (Note, p. 111). Professor Stevelly, of Belfast, who 

 has long given special attention to this part of the subject, adopts the 

 view that " the constituent particles are minute spherules, but not 

 vesicles." He refers their suspension to two causes — "the extreme 

 slowness of descent through the air of such exceedingly minute particles, 

 and the repulsive action of the electrical atmospheres of these particles 

 upon the ambient air {Fourth Report British Association, 1834). The idea 

 of electrical atmospheres originated, we believe, with Mr. Henry Eeles, of 

 Lismore, in Ireland, about the year 1750. His views on this and other 

 collateral subjects were communicated to the Royal Society {Philo- 

 sophical Transactions, 1752), and afterwards published in a small octavo 

 volume, under the title of Philosophical Essays, Dublin, 1771. He 

 supposed that the vapour ascended in vesicles, enveloped by such an 

 atmosphere, but descended in drops, receiving accretions as they fell. 

 This branch of meteorology is still involved in great obscurity — as well 

 the internal structure, mutual dependence of the parts, and mode of 

 suspension of clouds, as the entire subject of atmospheric electricity. 

 There can liardly be a doubt that some such agency as Mr. Eeles sug- 

 gested is actively at work in the production of rain and hail, especially 



