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nearer and nearer to each other, and, approaching towards one common 
centre, will gradually coalesce in their passage. 
Doctor Franklin has related a most ingenious experiment, which eluci¬ 
dates the formation of rain as thus described. 
Take round pieces of pasteboard of two inches diameter; from the 
centre and circumference of each of them suspend, by fine silk threads 
eighteen inches long, seven small balls of wood, or seven peas equal in 
bigness; so will the balls appending to each pasteboard form equal equi¬ 
lateral triangles, one ball being in the centre, and six at equal distances 
from that and each other; and thus they represent particles of air. Dip 
both sets in water, and, some adhering to each ball, they will represent air 
loaded. Dexterously electrify one set, and its balls will repel each other to 
a greater distance, enlarging the triangles. Could the water supported by 
the seven balls come into contact, it would form a drop or drops so heavy as 
to break the cohesion it had with the balls, and so fall. 
Let the two sets then represent two clouds, the one a sea cloud electrified, 
the other a land cloud; bring them within the sphere of attraction, and they 
will draw towards each other, and you will see the separated balls close thus:— 
The first electrified ball that comes near an unelectrified ball, by attraction, 
joins it and gives it fire; instantly they separate, and each flies to another 
ball of its own party, one to give, the other to receive fire; and so it pro¬ 
ceeds through both sets, but so quick as to be, in a manner, instantaneous. 
In their collision they shake off and drop their water, which will represent 
rain. 
But it rarely happens, that a land cloud is equal in magnitude to one 
raised from the sea; consequently the rain produced by their union, will be 
piopoitionably lighter in the upper, and heavier in the lower regions of the 
atmosphere, as the electric matter is more or less gradually diffused. 
When an electrified cloud, without mixing with another cloud, or losing 
part of its electric fire, becomes specifically heavier than the atmosphere, by 
cold, or some local change in the density of the air, it will descend at first 
perhaps m a mist; or will form, as it approaches nearer to the earth, and is 
less replete with the electric fluid, a light shower of rain. 
In confirmation of this doctrine is the discovery of the late Dr. Heberden, 
which was read before the Royal Society, Dec. 1769 . This amiable and 
sagacious physician writes as folloAvs: 
