123 
south, and precipitates it in showers ; or, in more extreme 
cases, in storms of rain. 
If I do not mistake, Sir John Ross describes the aurora 
in high northern latitudes, in winter, as being frequent, 
almost constant, as well as very near the Earth. 
The cause of this seems to be the opposing currents being 
then close to the point where they must necessarily coine 
into contact, and where even the smallest portion remaining 
of the opposite electricity must be discharged. 
Sir John also speaks of the waving motion being accom- 
panied by a very perceptibly audible sound. This may be 
aided by the known property of highly condensed air to 
transmit sound to unusual distances • and I have a strong 
impression of having myself heard a sound similar to that 
produced by the waving of a flag, when the aurora was 
playing actively. 
As far as it is known, the identity of the light flickering 
clouds, above described as seen by day, and of the aurpra as 
visible at night, is a neiv observation ; and the following 
opinions, expressed by men of great eminence in meteoro- 
logical science, while in no instance identical with the 
J&ti # ' ' " 1 " 
theory here proposed, may it appears, be not unfairly 
adduced in its support. Beccaria, in the last century, 
offered a suggestion that there was a constant circulation of 
the electric fluid between north and south ; but he gave an 
explanation different from the foregoing of the planner 
in which he conceived it might take place. Herschel 
states his idea, in general terms, that the northern lights are 
produced by the electric fluid ; and Admiral Fitzroy, in his 
report referred to above, “ On the Polar and Equatorial Air 
Currents,” has the following passage : — •“ We find here that 
the main currents, polar and equatorial, have very different 
electrical characteristics — one, the polar, being always plus ; 
the other, always minus ; — if pure, unmixed ydth the 
polar.” 
