Natural History. 489 



b;\'^rora Borealia seen in the Day-time at Canonmills. — The 

 morning of Sunday, September 9th, was rainy, with a light gale 

 from the N.E. Before mid-day the wind began to veer to the 

 west, and the clouds in the north-western horizon cleared away : 

 the blue sky in that quarter assumed the form of the segment of 

 a very large circle, with a well-defined line, the clouds above con- 

 tinuing dense, and covering the rest of the heavens.' The centre of 

 the azure arch gradually inclined more to the north, and reached 

 an elevation of nearly 20®. . In a short time very thin fleecy clouds 

 began to rise from the horizon within the blue arch ; and through 

 these very faint perpendicular streaks, of a sort of milky light, 

 could be perceived shooting; the eye being thus guided, could 

 likewise detect the same pale streaks passing over the intense 

 azure arch, but they were extremely slight and evanescent. Be- 

 tween nine and ten in the evening of the same dajs the aurora 

 borealis was very brilliant: so that there is no reason to doubt 

 that the azure arch in the morning, and the pale light seen shoot- 

 ing across it, were connected with the same phenomenon. — Jame- 

 son's Jour. 1827, p. 378. 



6. Aurora Borealis in Siberia. — Baron Wrangle says, that in 

 Siberia, when shooting stars pass across the space occupied by 

 polar lights, fiery beams suddenly arise in the place traversed by 

 the shooting star: further, that when a polar beam rises high 

 towards the zenith, the full moon also being high, it gradually 

 forms a luminous circle around the moon, at a distance of 20° or 

 30° from her, remains in this form for a short time, and then dis- 

 appears. 



7. On the Presence of Ammonia in Argillaceous Minerals. — Being 

 engaged in the examination of different specimens of gypsum, 

 M. Bonis observed, that traces of ammonia were evident in one 

 containing much argillaceous matter. The peculiar odour common 

 to argillaceous minerals when breathed upon, was very striking in 

 this specimen of gypsum ; when a portion of it was moistened with 

 solution of potash, and muriatic acid brought near, white vapours 

 were produced, and reddened litmus paper was very quickly ren- 

 dered of a blue colour in its vicinity. 



It was now suspected that all mineral substances, emitting an 

 argillaceous odour, contained ammonia ; a great number of speci- 

 mens were tried, being moistened with solution of caustic potash, 

 and examined by litmus paper. In no case was ammonia absent, 

 and, with common clay it continued to be evolved for more than two 

 days. Amongst the substances tried, were pipe clay, other cjays, 

 numerous gypsums, Paris plaster, steatite, &c. The antiquity of 

 the mineral seemed to have no relation to the ammonia. 



M. Bouis concludes that, in all cases, the argillaceous smell of 

 minerals is connected with, and dependent upon, the presence of 

 ammonia, the latter being the vehicle of this particular odour. — 

 Annales de ChimiCy xxxv. 333. 



