384* Meteorology, 



soil is gradually washed away by rains, brooks, &g., and that the rock is by 

 these means frequently, if not always, laid bare. They say farther, that 

 detritus cannot be carried from places which are level ; but, if the sea is 

 lower than the land, all the land may be considered as a series of staired 

 plains, if I may use the expression ; and at every common section of a decli- 

 vity and a plain, there is a tendency to efface the latter, by invading its 

 boundaries or destroying its level. — J, R, 



B6rax and Soda are recommended, as tests for manganese, by Berzelius, 

 in his treatise on the blowpipe ; the former giving a purple, and the latter, 

 on platina foil, a pale greenish blue glass. Soda, by itself, appears incapable 

 of dissolving a sufficient quantity of manganese to impart to the glass a 

 strong blue tint. Borax dissolves manganese easily, but the purple suit 

 sometimes does not appear till after the addition of nitre, and is very 

 obscure when the assay contains a large proportion of iron ; but the addition 

 of a small quantity of soda to the assay, fused with borax on platina 

 wire, readily brings out the purple colour, rather more inclining to blue 

 than when borax alone is used; and, finally, as more soda is added, it 

 changes to a fine deep blue, that cannot be mistaken. — M, 



Art. V. Meteorology, 



Moisture of Climate influenced by Trees. — The cutting down of forests, 

 particularly on high grounds, has been remarked to diminish the quantity 

 of rain, by diminishing, it is supposed, the attraction for clouds. The fact, 

 however it may be explained, has been ascertained on a large scale in Ame- 

 rica. In Kentucky, for example, many brooks are pointed out which now 

 fail in summer, a thing which was unknown 20 or 30 years ago. In New 

 Jersey, where the woods have been more extensively cleared, some streams 

 have been altogether dried up. On the contrary, many streams in the 

 United States have rather increased since the clearing of the woods ; be- 

 cause, though the quantity of rain may be possibly diminished, the compact 

 bed of forest leaves formerly retained the water on the surface, and exposed 

 it to rapid evaporation ; whereas, the tillage which has been introduced, 

 allows the water to penetrate to some depth, and to afford a more perma- 

 nent supply for springs and streams. — J. R. 



Sea Air. — The atmosphere, in the vicinity of the sea, usually contains a 

 portion of the muriates over which it has been wafted. It is a curious fact, 

 but well ascertained, that the air best adapted to vegetables is pernicious to 

 animal life, and vice versa. Now, upon the sea-coast, accordingly, animals 

 thrive, and vegetables decline. {Hariuood's Southern Coast.) 



To ascertain the Course of the Air, when there is not any perceptible Wind 

 blowing. — Place a basin of water in a free exposure, throw a red hot cin- 

 der into it, and observe how the smoke which it produces inclines. Sailors 

 throw a piece of live coal into the sea for the same purpose ; and also wet 

 a finger, hold it up in the air, and then by feeling which part becomes first 

 (by evaporation) cool, they judge of the direction of the current of air. An 

 instrument on the last principle has been invented by Dr. B. M. Forster, and 

 described in the London Journal of Arts and Sciences for May. {Mec. Mag., 

 vol. ix. p. 272.) 



Extraordinary Fall of Rain. — At Joyeuse, in the department of the 

 Ard^che, during October, 1827, 36 in. in depth fell within eleven days ; and 

 on the 9th of that month, 29J in. fell within the space of two hours. During 

 this excessive fall of rain, the barometer remained nearly stationary, at two 

 or three lines below the mean altitude, notwithstanding the continuation 

 of the most violent thunder and lightning during the whole time. (Annates 

 de Chimie.) 



