Intelligence and Miscellaneous Articles. 161 



same aspect as the obscure train produced by the cloud in a very 

 different region of the sky. They were distinguished from it how- 

 ever by tlieir size, which was much less ; each extended only a 

 degree in diameter. They were displaced in a perceptible manner 

 toward the south-east, in proportion as the sun declined toward the 

 horizon. They continued to be visible at least two hours, to my 

 comj)anions as to me. But we knew not to what cause to attribute 

 them. No perceptible obstacle in the immense panorama which we 

 commanded could produce shadows in their direction, and serve thus 

 to explain their presence. 



The disposition of the atmospheric vapours in layers, may some- 

 times engender appearances which are confounded with those of 

 shadows. Long observation, and the variations of tint of the dark 

 bands, serve to avoid the error. An example of these false shadows 

 was presented to me two days after from the i:)lateau of the Barillette. 

 A few minutes before sunset, the ground of the sky assumed a very 

 marked gray colour, trenched upon by three horizontal bands tole- 

 rably long, of a more leaden colour, and which converged toward the 

 east. These bands, which would have presented an inverse distribu- 

 tion if they had been parts of the space destitute of light, became 

 gradually of a bright rose colour a few minutes after the twilight 

 came on. They were therefore only formed by a slight haze, sus- 

 pended at a great height in the atmosphere. — Bibliotheqiie Univer' 

 selle, September 1849. 



ON THE ARTIFICIAL FORMATION OF CORUNDUM AND DIASPORE 

 BY THE WET METHOD. BY M. II. DE SENARMONT. 



Not long since I laid before the Academy some experiments upon 

 the artificial production of several kinds of minerals l)y the wet me- 

 thod, under the combined influences of heat and great pressure ; and 

 I endeavoured to explain in this manner the formation of a peculiar 

 class of metalliferous deposits, principally formed from liquid agents. 



Various minerals belong to another class of deposits where the 

 influence of gaseous agents appears to have predominated, where 

 water, which has played an important part in these phcenomena, must 

 have acted principally in the state of vapour. It must not, however, 

 be. expected that we should find a well-marked line of demarcation 

 between these two kinds of formations. Those substances which 

 mineralize thermal waters, frequently perhaps spring from depths 

 below the earth's surface in the form of volatile compounds; the liquid 

 and gaseous agents have been present in very variable proportions, 

 and the phsenomena musthave presented numerous intermediate stages 

 between their two extreme limits. It is moreover very difficult, even 

 in a chemical point of view, to imagine the action of water to be very 

 different when filling the same space in the state of a very strongly 

 heated liquid, or when saturating it in the state of vapour under enor- 

 mous pressure. 



Numerous kinds of minerals must therefore be formed, almost in- 

 differently, under one or the other of these conditions. 



