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 occm'. 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, Avhether Mr. 

 Christie had taken any notice of the very remarkable aurora 

 which occurred 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 

 vacuo 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. Abram had no doubt whatever, but that the 

 aurora was a magneto-electrical effect ; and described an appara- 

 tus which he had contrived in order to illustrate this. 



Mean ternperature at Plymouth^ England. — The mean tem- 

 perature of two years, from 17,520 observations, is 52.90 ; that 

 of five years, from 43,800 observations, 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- 

 ous, and, to him, entirely inexplicable property of light. While 

 examining the solar spectrum formed in the focus of an achro- 

 matic telescope, after the manner of Frauenliofer, he placed a thin 



