6 Temperature of the Terrestrial Globe. 



Thus the solar heat has accumulated in the interior of the globe 

 and is there continually renewed. It penetrates the parts of the 

 surface near the equator, and is dissipated through the polar regions. 

 The first question of this kind which has been submitted to the cal- 

 culus, is found in a memoir which I read to the French Institute, at 

 the close of the year 1807, Art. 115, page 167. This article is 

 deposited in the archives. I then took up this first question to ex- 

 hibit a remarkable example of the application of the new theory ex- 

 posed in the memoir ; and to show how the analysis points out the 

 tract followed by the solar heat in the interior of the earth. 



If now we replace this exterior envelop of the earth, whose points 

 are not sufficiently deep to have a fixed temperature, we remark an 

 order of facts more compound, the complete expression of which is 

 given by our analysis. At a moderate depth, as three or four me- 

 ters, the temperature observed does not vary during each day, but 

 the change is very perceptible in the course of a year ; it varies and 

 and falls alternately. The extent of these variations, that is, the 

 difference between the maximum and minimum of temperature, is 

 not the same at all depths ; it is inversely as the distance from the 

 surface. The different points of the same vertical line do not arrive 

 at the same time at the extreme temperatures. The extent of the 

 variations, the times of the year, which correspond to the greatest, 

 to the mean, or to the least temperatures, change with the position 

 of the point in the vertical line. There are the same quantities of 

 heat which fall and rise alternately ; all these values have a fixed 

 relation between themselves, which are indicated by experiments 

 and expressed distinctly by the analysis. The results observed are 

 in accordance with those furnished by the theory ; no phenomenon 

 is more completely explained. The mean annual temperature of 

 of any point whatever in the vertical line, that is, the mean value of 

 all those which might be observed in the course of a year, at this 

 point, is independent of the depth. It is the same for all points of 

 the vertical, and consequently that which would be observed imme- 

 diately below the surface ; it is the fixed temperature which exists 

 at great depths. 



It is evident that in the enunciation of this proposition, we make 

 no account of the internal heat of the globe, and those accessory 

 causes which would modify this result in a particular place. Our 

 principal object is to ascertain general phenomena. We have be- 

 fore remarked that the different effects can be separately considered. 



