De la Rive on the Aurora Borealis. 357 
solar rays causing evaporation from the waters of the seas, or the 
vegetation of the land. It is probable that both causes act: yet 
Iam inclined to regard the first as most general and most con- 
stant. But this is of little importance here: the fact of the con- 
stant charge of positive electricity in the atmosphere, and of 
hegative electricity in the earth, is abundantly proved, and this 
is sufficient for our explanations. 
his constant production of the two electricities must necessa- 
rily be attended by a recomposition or neutralisation ; otherwise 
the contrary’ electric states woul ire an infinite tension, 
disturbances and consequently fewer storms; and at the same 
the air for the hours of the day, and days of the year. Hence 
it is difficult to deduce from these observations even the intensity 
of the atmospheric electricity for any given moment, seeing that 
it is impossible to separate this original intensity from the de- 
bag more or less decided which the electric registers may mani- 
est. f 
Let us now pass to the second mode of neutralisation of the 
two electricities, which I regard as normal and regular. 
he positive electricity, with which the upper beds of the at- 
mosphere are charged, will traverse them freely, because of their 
high state of rarefaction. But in the polar region, where the in- 
tense cold constantly condenses the aqueous vapors, it finds a 
