68 Analj/ses of Booh. [July, 



2d. The prevailing winds were from the eastward and west- 

 ward ; and the arches usually extending from NW to SE ; 

 the influence of the wind might have been mistaken for their 

 lateral motion. 3d. The northerly winds, acting from the same 



2uarter as the direct motion, were confounded with it. 

 .astly, the southerly winds, which were not common, always 

 filled the atmosphere with clouds, so that the Aurora was not 

 Visible. Perhaps, after all, the Aurora of the 27th of April was 

 nearer to the earth than any other which we saw.'* 



" On the 11th of March, at 10'' p.m., a body of Aurora 

 rose NNW, and after a mass of it had passed to E by S the 

 remainder broke away, in portions consisting each of several 

 beams, which crossed about 40^ of the sky with great rapidity. 

 We repeatedly heard a hissing noise, like that of a musket- 

 bullet passing through the air, and which seemed to proceed 

 from the Aurora ; but Mr. Wentzel assures us, that this noise 

 was occasioned by severe cold, succeeding mild weather, and 

 acting upon the surface of the snow, previously melted in the 

 sun's rays. The temperature of the air was then 35°, and on 

 the two preceding days, it had been above zero. The next 

 morning it was — 42°, and we frequently heard a similar noise. 

 Mr. Hearne's description of the noise of the Aurora agrees 

 exactly with Mr. Wentzel's, and with that of every other per- 

 son who has heard it. It would be an absurd degree of scep- 

 ticism to doubt the fact any longer ; for our observations have 

 rather increased than diminished the probability of it." P. 584, 

 585. 



" The common cork-ball electrometer not having on any oc- 

 casion given signs of a charge, I tried the following experi- 

 ment, in order to attain further evidence on the subject. A 

 brass needle was attached to a compass card, and balanced on 

 a copper pivot in a wooden box. It was about four inches in 

 radius, and a copper arch of 60° to that radius, was fixed at 

 one end of the box, which was closed by a wooden slide, and 

 paper pasted over every crevice to exclude the air. To 

 give it the same advantages for conducting electricity as the 

 compass boxes (which are made of brass), 1 introduced an iron 

 wire, eight inches in length, perpendicularly through the lid, 

 in such a manner, that its lower extremity was in a horizontal 

 plane with the needle ; and a pane of glass at that end of the 

 lid, enabled me to see into the interior of the box. Having 

 previously ascertained that it contained no magnetism, the in- 

 strument was placed, on the 2d of May [1821], on a covered 

 shelf, at the outside of the house, in a position nearly east and 

 west ; the brass needle being 25' from the conductor, and a 

 small ^lass bubble adjusted on the box, in order to prevent its 

 otherwise unperceived movement. At 12'* p. m. I examined 

 the needle, and found its position unaltered. No Aurora was 

 then visible, but one was afterwards seen by Mr* Franklin i 



