ON AQUEOUS AND IGNEOUS METEOKS. 713 



collecting rain are perhaps chiefly (derived from the ascending currents which 

 they occasion, and by which the air saturated with moisture is carried to a 

 higher and a colder region. 



The Abyssinian rains arethecausesoftheinundationoftheNIle; theylastfrom 

 April to September ; but for the fiist three months the rain is only in the night- 

 The inundation, in Egypt, begins at present about the 17th of June; it increases 

 for 40 days, and subsides in the same time; but the ancient accounts, as well 

 as some modern ones, assign a longer duration to it. The river Laplata rises 

 and falls at the same times as the Nile. The Ganges, the Indus, the Euphrates, 

 the river of Ava or Pegu, and many other large rivers, have also considerable 

 inundations at regular periods. In many other countries there are seasons at 

 which the rains seldom fail to recur; and sometimes the periodical rains are 

 different in different parts pf the same country. Thus the coast of Malabar, 

 which is to the west of the Gate mountains, or Gauts, enjoys summer 

 weather, without rain, from September to April, while that of Coromandel* 

 which is on the eastern side, experiences all the rigours of its winter; being at 

 this time exposed to the influence of the north east trade wind. Vicissitudes 

 of a similar nature are also observed on the north and south sides of the island 

 of Jamaica. The mean fall of rain in London is about 23 inches; at Exeter, 

 which is nearer to the Atlantic, 33; the average of England and Wales is 31. 



The evaporations and precipitations, and probably also the condensations 

 and expansions, which take place on a large scale in the atmosphere and in 

 the clouds, cannot fail of producing changes in their electrical qualities; 

 and these changes appear to be the principal sources of the phenomena of 

 thunder and lightning. The clouds, when electrified, being more or less 

 insulated by the interposition of the air, exhibit attractive and repulsive 

 effects, and are discharged by explosions, either among themselves, or com- 

 municating with the earth, in the same manner as bodies which have been 

 electrified by artificial means; they also sometimes produce, in the neighbour- 

 ing parts of the earth, and in the animals on its surface, a state of induced 

 electricity ; and in this case the returning stroke, or the sudden restoration 

 of the equilibrium, when the electricity of the nearest clouds is imparted t& 

 the more remote, may be fatal, without any appearance of an immediate 

 discharge, at the place where the animal stands. 



