Atmosphere. 101 



both of the solids and fluids ; and from 

 the want of this due pressure it is that on 

 the summits of lofty mountains the blood 

 often issues from the pores of the skin, 

 or from the lungs. 



Various attempts have been made to 

 ascertain the height to which the atmos- 

 phere is extended all round the earth. 

 These commenced soon after it was dis- 

 covered by means of the Torricellian tube 

 that air is endued with weight and pres- 

 sure. And had notthe air an elastic pow- 

 er, but were it every where of the same 

 density, from the surface of the earth to 

 the extreme limit of the atmosphere, like 

 water, which is equally dense at all depths 

 it would be a very easy matter to deter- 

 mine its height from its density and the 

 column of mercury it would counterbal- 

 ance in the barometer tube : for, it having 

 been observed, that the weight of the at- 

 mosphere is equivalent to a column of 

 thirty inches or 2-| feet of quicksilver and 

 the density of the former to that of the 

 latter, as 1 to 1104O; therefore the height 

 of the uniform atmosphere would be 

 11040 times 2 feet, that is, 27600 feet, 

 or little more than 5^ miles. But the air, 

 I 



