188 REACTION OF THE INTERIOR OF THE EARTH 



separate actual observations from the theoretical con- 

 clusions which have been based upon them. The ob- 

 ject we aim at, enounced in its greatest generality, is 

 a threefold one: the distribution of heat, in the ac- 

 cessible part of the earth's crust, in the aqueous cover- 

 ing (the ocean), and in the atmosphere. In the liquid 

 and gaseous coverings of the globe, an opposite variation 

 of temperature takes place in the vertical direction. 

 In the solid parts of the globe, the temperature in- 

 creases with increasing depth ; the variation being here 

 the same in direction (though the ratio is very different) 

 as in the atmospheric ocean, in which elevated plateaus 

 and variously shaped mountain summits represent shoals 

 and submarine rocks. We are acquainted by direct 

 experiment with the distribution of heat in the at- 

 mosphere, geographically or in different latitudes and 

 longitudes, and hypsometrically or at different amounts 

 of vertical elevation above the level of the sea. This 

 knowledge is, however, almost wholly confined to the 

 near vicinity of the solid or liquid surface. Scientific 

 and systematically arranged investigations, by means of 

 aerostatic explorations of the aerial ocean beyond the 

 immediate proximity of the disturbing influences of the 

 earth, are still so much too few in number, that they 

 have for that reason been little capable of affording the 

 requisite numerical data for mean conditions. In re- 

 gard to the decrease of temperature in the depths of 

 the ocean, observations are not wanting; but currents 

 bringing water from different latitudes and depths, and 

 of different densities, interpose almost greater obstacles 

 to the attainment of general results than do the currents 

 of the atmosphere. The thermic conditions of the two 



