20 British Association for the Advancement of Science. 
hope, that observations of the highly interesting phenomena of 
the aurora would be entered upon by members of the British As- 
sociation, who might have more time at their command than his 
own avocations allowed him for such observations. 
Mr. Stevelly stated, that the dark cloudy appearance during the 
aurora was so characteristic, that on one or two occasions, having 
seen, just before sunset, these scattered black clouds, he was led 
to anticipate that an aurora would ensue, which accordingly man- 
ifested itself when it grew dark; and a friend, since he came to 
Liverpool, had boasted that he could unfailingly predict an au- 
rora on the evening of the night on which it was to occur. He — 
had mentioned this to Prof. Christie, who said that his.own ex- 
perience had been precisely similar.—Sir David Brewster said, 
that, by an analysis of the light of the aurora borealis, he had 
proved that it was direct light, and had never suffered either re- 
flection or refraction.—Sir. W. Hamilton inquired, whether Mr. 
Christie had taken any notice of the very remarkable aurora 
which cecurred on the 18th of last February.—Prof. Christie 
said he had observed it. The object, however, of his present 
communication, was to turn attention to the occurrence of the 
aurora in summer.—Mr. Snow Harris trusted that a wide line of 
distinction would be drawn between electrified luminous clouds 
and the true aurora. He also wished attention to be turned to 
the. difference between magnetic needles when suspended in 
uo and in the open air. He had exhausted a very tall glass — 
receiver, and by electrifying it, caused a very brilliant display re- 
sembling the aurora. This notably affected a needle suspended 
near it in the open air; but a needle suspended in vacuo was not 
at all effected.—Mr. Absent had no doubt whatever, but that the 
aurora was a magneto-electrical effect ; and described an areas 
tus which he had contrived in order * illustrate this. 
Mean temperature at Plymouth, England.—The mean tem- — 
perature of two years, from 17,520 observations, is 52.90; that 
of five years, from 43,800 chocwvationsi: is 52.45. 
New property of Light.—Sir David Brewster then gave an ac- 
count of a new property of light discovered by him. He ob- 
served, that his attention had lately been drawn to a very curi- 
is, and, to him, entirely inexplicable property of light. While 
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