Intelligence and Miscellaneous Articles. 387 



tity of distilled water alone. The fact was ascertained in the fol- 

 lowing manner : — The author, having procured two small porcelain 

 vessels, exactly of the same size, introduced into one of them 300 

 grains of distilled water, and into the other a small quantity of sili- 

 ceous sand, over which 300 grains of water were poured, so as not 

 only to saturate the sand, but also to leave a layer of water of about 

 one- tenth of an inch in thickness over and above its surface. At 

 the end of five days, it was observed that the water standing alone 

 had lost 184 grains of its previous weight, while the water mixed 

 with the sand had lost no less than 196 grains. The average dif- 

 ference, resulting from a series of experiments, was 7| per cent, in 

 favour of the more rapid evaporation of water mixed with sand com- 

 pared to that of water standing alone. If the experiment be made 

 with glass or metallic vessels, the difference is only about 4 \ per cent. 



6. The last result which we shall mention, and which may be re- 

 garded as a direct consequence of the preceding one, is the follow- 

 ing : — Water mixed with sand remains habitually at a slightly lower 

 temperature than an equal surface of water standing alone. The 

 difference varies to a certain extent, according to the nature of the 

 vessels in which the experiment is performed, never however ex- 

 ceeding \ a degree Centigrade. It is greater, when the comparison 

 is made between water and wet sand placed in two similar metallic 

 vessels, than when they are placed in porcelain or glass vessels ; in 

 the latter case it seldom exceeds o, l to 0°'2, 



The author concludes by remarking, that the foregoing result 

 tends to confirm an opinion expressed some time since by Professor 

 De la Rive, in a letter to M. Arago, published in the Comptes Rendus 

 de VAcademie des Sciences for October 1851. In this letter, M. De 

 la Rive attributes the sudden appearance of vast glaciers in divers 

 parts of Europe to a temporary refrigeration produced at the period 

 of the elevation of the most recent European strata, by the evapora- 

 tion of the water with which they were previously covered. If, as 

 the author's experiments tend to show, evaporation takes place more 

 rapidly from water mixed with sand, earth, or any similar substance, 

 than from a surface of clear water, it becomes natural to conclude, 

 that the cold produced by evaporation from the recently elevated 

 and still humid strata, must have been greater than that resulting 

 from the evaporation of the sea or freshwater lake which covered 

 them previously to a great depth. — Bibliotheque XJniverselle, April 

 1853. 



ON AN UNUSUAL LUMINOUS APPEARANCE IN THE SKY. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, Sidmouth, Oct. 19, 1853. 



I have been favoured by a lady (Mrs. Bennett) with some account 

 of a meteoric appearance in the sky, which she witnessed on the 

 evening of the 2nd of September last at Exeter. I am induced to 



