Royal Society. &lfB. 



Paper C. The horizontal intensity, with an example. 

 Paper D. The declination, with an example. 

 Paper E. The latitude, with an example. 

 Paper F. The longitude from moon-culminating stars, 

 I have the honour to be. Sir, 



Your most obedient Servant, 

 Madras, C M. Elliot, 



August 6, 1819. Captain Madras Engineers, 



Jan. 31. — " An account of a remarkable Aurora Borealis seen at 

 Montreal on the 13th of August 1849." By Mr. Thomas M«=Ginn. 

 Communicated by Thomas Bell, Esq., Sec. R.S., &c. 



The author having witnessed a singular aurora on the 13th of 

 August, in this communication gives a description of the phaeno- 

 menon. He states that, on the evening in question, the whole north- 

 ern hemisphere was screened by thick dark clouds, which, though 

 very small, were closely packed together. Shortly after sunset (7'* 

 34"") it became quite dark, and at 8 o'clock the existence of the 

 meteor was indicated by a mellow luminous tinge which appeared 

 through the openings of the clouds in the north. 



About half-past eight a similar luminous glow was observed 

 through the clouds which were fast disappearing in a heavy dew. 

 This light appeared like a belt of 2° broad, extending across the 

 sky from a point almost due east directly to the west, and reaching 

 within 5° or 6° of the horizon. As the clouds disappeared, which 

 they did very rapidly, the true character of the aurora became more 

 perfectly developed. In the north the usual dark arch from which 

 the columns of light ordinarily appear to issue, was for the greater 

 part of the time wanting; and the luminous columns seemed to rise 

 from the earth, extending upwards occasionally to the pole star, 

 beyond which no trace of them was visible. A brown vapoury 

 cloud, the only one now visible, extended along the horizon from N.N.F^. 

 to a ie\f points south of east, and maintained apparently a motion- 

 less position, the lower part appearing to rest upon the earth, and 

 the upper edges, which seemed uniform, rose about 6° above the 

 horizon. Immediately in the east, and apparently issuing from this 

 cloud, rose the belt or zone of light already noticed, forming a mag- 

 nificent arch. The light emitted from this zone was of a milky 

 whiteness, and the matter of it seemed to be much more compact 

 than any portion of an aurora ever seen by the author ; but imme- 

 diately in the zenith, where it intersected the Milky Way, it ap- 

 peared to be far less compact. At this point, where alone motion 

 was observable, a constant current w-as seen, presenting the appear- 

 ance of light fleecy clouds driven by a strong wind, and following 

 each other in such close succession as to appear in contact. This 

 stream of the aurora was maintained undiminished for more than an 

 hour, during which time the eastern part of the zone did not appear 

 to lose either in volume or brilliancy, nor did the western seem. to 

 gain in either of these respects. After an hour, the dark cloud 

 seemed to diminish slowly, and with it the zone began to lose its 

 brilliancy. In about another hour this cloud and also the zone, 



