-1859] WRITINGS OF JOSEPH HENRY. 49 



of the increased pressure, and with this the original tempera- 

 ture will be restored. 



This principle, as we shall see hereafter, is of great im- 

 portance in the study of the peculiarity of the temperature 

 of the western portion of the territory of the United States. 

 We have said that every pound of air, from the bottom of 

 the aerial ocean to its surface above, contains at least an 

 equal quantity of heat; and this was the inference of Dal- 

 ton. From the investigations of Poisson and others it ap- 

 pears that the absolute quantity of heat, pound for pound, 

 slightly increases rather than diminishes as we ascend; and 

 this seems necessary to the stability of the equilibrium of 

 the atmosphere as a whole. If the amount of heat were 

 greater in the lower strata than in the upper, the equilibrium 

 would be unstable, and an inversion would tend constantly 

 to take place. An equal quantity of heat, (pound for pound,) 

 as we ascend, would produce an indifferent equilibrium, 

 while an increased amount in the order of ascent, would 

 produce a stable condition of the atmosphere, such as that 

 which really exists. The question however has not yet been 

 fully settled, although it is an important one having a bear- 

 ing on the explanation of many meteorological phenomena. 



Another question of much interest is the exact law of 

 diminution of temperature as we ascend into the air. Were 

 this actually known, we could reduce to the same level all 

 the observations which are made in a country; and thus, in 

 addition to the astronomical effects, we could eliminate those 

 due to altitude, and present the remainder as results which 

 are due to the other conditions producing the peculiarities 

 of climate. In order however to apply the law with pre- 

 cision in this way, it is desirable that it should be deter- 

 mined from observations made by ascents in balloons or at 

 points of different heights on isolated mountain peaks. 

 Relative observations made for this purpose on the top and 

 at the base of mountain systems of considerable width and 

 extent will probably give results involving the influence of 

 the mountain surface itself, which in turn would be some- 

 what affected by the direction of the prevailing wind and 

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