262 Writings of Joseph henrt. [1855- 



In still weather it indicates the same amount of water as the 

 larger gauges, but when the wind is high it receives more 

 rain, for on account of its small size the force of the eddy 

 which is produced is much less in proportion to the momen- 

 tum of the drops of water. This gauge, which has been 

 copied from one introduced by Mr. James Stratton, of Aber- 

 deen, may be still further improved by cutting a hole of the 

 size of the cylinder into a circular plate of tin of 4 or 5 inches 

 in diameter, and soldering this to the cylinder like the rim 

 of an inverted hat, three or four inches below the orifice of 

 the gauge. 



The effect of the wind in disturbing the level of light snow 

 in the vicinity of buildings illustrates the general princi- 

 ples which we have endeavored to explain. When a rapid 

 current of air is obstructed by a building the acceleration 

 of its velocity on the side of the eddy is marked by the re- 

 moval of the snow to a considerable distance. Indeed all 

 the phenomena we have mentioned in regard to rain are 

 illustrated by the extraneous motion given to the particles 

 of descending snow. 



Constitution and phenomena of the compound atmosphere. — 

 From the principles we have endeavored to explain, we may 

 now readily infer what would be the general effects if the 

 earth were surrounded with an ocean of water and devoid 

 of an atmosphere. At first sight it might appear that all 

 the water of the ocean would immediately pass into vapor ; 

 but, on a little reflection, it will be seen that this would not 

 be the case. A definite amount of vapor would be formed, 

 which by its pressure on the surface of the water would pre- 

 vent any further evaporation, provided the whole globe and 

 the space around it were of uniform and constant tempera- 

 ture. 



A portion of vapor would rise from the water and would 

 expand as it rose until the upper atoms were so far separated 

 that their repulsion would become insensible and they would 

 be retained as an appendage to the earth merely by their 

 weight. The upper layer of vapor would press on the next 

 lower, and this on the next, and so on with accumulating 



