166 Miscellaneous Intelligence. 



The hot and dilated air contained in those intervals not being 

 hermetically retained, will gradually escape ; but this renewal 

 of the internal air must take place very slowly, so that the 

 temperature of the cloud will always be above that of the neigh- 

 bouring air, and this ascending current of air, by the mere 

 friction of its parts against the particles of the cloud, will tend 

 to raise it, and that with the more energy as it is more rapid. 



During the night the cloud is deprived of the solar rays, and 

 its temperature should diminish, but it will still receive warm 

 rays from the earth ; and if it is very thick, or of great depth, 

 its temperature can diminish only slowly. Experience proves 

 directly,^that clouds during the night are warmer than the air 

 surrounding them, inasmuch as they send us more calorific rays- 

 Supposing even that the difference of temperature was much 

 less by night than by day, still the clouds should descend with 

 extreme slowness after sunset, because of their immense extent 

 of surface, relative to their weight : it is a cause which, without 

 referring to their elevation, must contribute powerfully to their 

 suspension, and the rise of the sun would again elevate them to 

 their former altitude, if winds or other atmospheric phenomena 

 have not Changed the conditions of equilibrium. Such an effect 

 may be produced by an augmentation or diminution of the par- 

 ticles of the cloud, or the intervals between them ; and the 

 changes in the temperature of the surrounding air, alter the 

 conditions of equilibrium, and consequently the height to which 

 the cloud may rise. There are without doubt, also, other causes 

 which contribute to the elevation and suspension of clouds, as 

 the ascending currents spoken of by M. Gay Lussac Cvol. xiv. 

 p. 446). I do not purpose to consider all the causes, but merely 

 to indicate that which appears to me the most important. — 

 Bib. Univ. xxi. 255. 



2. Aerolite of Epinal. — The stone which fell in the neigh- 

 bourhood of Epinal, about three quarters of a league from La 

 Baffe, on the 15th of last September, has been examined chemi- 

 cally by M. Vauquelin. Like most aerolites, it was covered by a 

 fused black coat. Within, it was of a gray colour, with many 

 metallic points. Ground in a mortar, a great number of parti- 

 cles of metallic iron were separated, leaving an impalpable 

 earthy powder. 



From the quantity of metallic iron existing in this stone, it was 

 difficult to obtain a portion for analysis, which should give the 



