56t FOURTH REPORT — 1834. 



He allows that this effect of the coldness of the superior rain 

 enters for something into the aggregate of the causes of increase 

 by descent ; but that it is considerable or appreciable he does 

 not admit. 



He observes (and refers for further particulars to his work on 

 the Climate of London), that rain falls principally in two ways: 

 1 . By the condensation or collapsing of the mass of an elevated 

 cloud, (effected by the subtraction of the electrical atmosphere 

 of the cloud, or by the extension of the atmospheres of the 

 spherules of the cloud, through their mutual attraction, the 

 electrical charge now taking its seat upon the smaller surface 

 of a congeries of larger drops, as is manifest by the charge 

 these give to the insulated rod,) or, 2. By loss of heat in tlie 

 whole mass of air from which it is about to rain (this lowered 

 temperature being the actual cause of the rain), in which case 

 the separation of the water is effected precisely in the manner 

 of the precipitation of solids from a menstruum in which they 

 were held in solution. The nascent drops exist in every part 

 of the raining space, and find their way to the earth subject to 

 the small augmentation, by virtue of the lower temperature 

 found at greater heights above mentioned. 



In the first case the rain at the top of a building a7id the rain 

 at the ground are equal in amount ; in the second, there is an 

 augmentation in the lower strata, which so overbalances the 

 former case, both in frequency and amount, as to give the aver- 

 ages the character they exhibit. 



An attempt to connect some of the best-known Phcenomena of 

 Meteorology with established Physical Principles. By Pro- 

 fessor Stevelly, A.m., of Belfast. 



The author examines, in this point of view, the following 

 four points : 



1 . The nature and origin of clouds ; 



2. The production of rain, and some of its consequences ; 

 - S. The origin of wind from clouds or rain ; 



4. The formation of hail. 



1 . Nature and Origin of Clouds. — The author adopts the 

 opinion, that the constituent particles of clouds are minute 

 spherules, but not vesicles ; and refers the suspension of clouds 

 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. 



Clouds are stated to owe their origin to the excess of vapour 



