10O Atmosphere. 



varies at times from twenty-eight to thitv 

 ty-one inches, or about one tenth of the 

 whole quantity, it follows, that this diffe- 

 rence amounts to about a ton and a half 

 on the whole body of a man, which he 

 therefore sustains at one time more than 

 at another. On the increase of this natu- 

 ral weight, the weather is commonly fine, 

 and we feel ourselves what we call braced, 

 and more alert and active ; but, on the 

 contrary, when the weight of the air di- 

 minishes, the weather is bad, and people 

 feel a listlesness and inactivity about 

 them. And hence it is no wonder that 

 persons suffer very much in their health, 

 from such changes in the atmosphere es- 

 pecially when they take place very sud- 

 denly. 



The weight of the atmosphere has great 

 influence on a number of physical pheno- 

 mena. It compresses all bodies, and op- 

 poses their dilatation. It is an obstacle 

 to the evaporation of fluids. The water 

 of the sea is by this cause preserved in its 

 liquid state, without which it would take 

 the vaporous form, as we see in the vacu- 

 um of the air pump. The pressure of 

 the air on our bodies preserves the state 



