2 Temperature of the Terrestrial Globe. 



2. It partakes of the common temperature of the planetary 

 spaces ; being exposed to the radiations from the innumerable stars 

 which surround the solar system. 



3. The earth preserves in its interior a part of that primitive heat 

 v^'hich it had at the time of the first formation of the planets. 



We shall separately examine each of these three causes, and the 

 phenomena which they produce. We will show, as clearly as we 

 are able in the present state of the science, the principal features of 

 these phenomena. For the purpose of giving a general idea of this 

 great question, and showing at a glance the results of our researches, 

 we present them in the following summary, which is in some meas- 

 ure a synoptic table of the contents of this article, and of several 

 which have preceded it. 



The solar system is situated in a region of the universe, every 

 point of which has a common and constant temperature, determined 

 by the rays of light and heat which proceed from the surrounding 

 stars. This low temperature of the planetary space, is a little below 

 that of the polar regions of the earth. The earth would have only 

 the same temperature with the heavens, were it not for two causes 

 which are concurring to heat it. One is the internal heat which it 

 possessed at its formation, a part of which only is dissipated through 

 the surface ; the other is the continued action of the solar rays, 

 which penetrate the whole mass, and produce at the surface, the 

 diversities of climate. 



The primitive heat of the globe has no longer any sensible effect 

 upon the surface : but it may be very great as we approach the 

 center. The temperature of the surface does not exceed by the 

 thirtieth of a centesimal degree, (y'j° Fahrenheit,) the lowest state 

 to which it can ever be reduced. At first it diminished very rap- 

 idly : but at present with the greatest slowness. 



The observations heretofore collected seem to show that the tem- 

 perature of different points of the same vertical line, is proportional 

 to the depth, and that this increase of temperature, as we advance 

 towards the center, is about one degree for every thirty or forty me- 

 ters. Such a result supposes a very high internal temperature. It 

 cannot proceed from the action of the sun's rays ; and it is naturally 

 explained by the heat which belonged to the earth at its formation. 



This increase of temperature, of about one degree for thirty-two 

 meters will not always remain the same. It gradually diminishes ; 

 but many ages must elapse before it can be reduced to half its pres- 

 ent value. 



