Temperature of the Terrestrial Globe. 21 



with the depth cannot be explained by the action of the solar rays. 

 We are obliged to seek for another cause applicable to continents 

 alone, and explanatory of these results. 



This cause is stated in my Physique de la Terre, printed in 1815, 

 namely the volcanic action which took place at the time of the for- 

 mation of the crust of the globe, and with a much greater energy 

 than is now developed. This ancient volcanic activity, is attested 

 by the tearing and overturning of rocks, by the great number of an- 

 cient volcanoes which are now extinct, and which are scattered over 

 almost ail latitudes and longitudes, by volcanic productions in large 

 and small masses, which are met with so frequently in places where 

 volcanoes are not to be found, among the number of which may be 

 mentioned basalt and its varieties ; which is so scattered that the cele- 

 brated Werner was led to believe that basalts the last product of the 

 general precipitation which formed continents that they had formerly 

 entirely covered and were wanting only in places from which the 

 breaking up and mechanical force of the revolutions had removed 

 them. 



The great force of volcanic action is demonstrated not only by 

 ancient volcanoes which are still active, but by new volcanoes which 

 are still forming upon continents and islands, in proximity to the 

 shores, but this force is manifested particularly by earthquakes which 



so often indicate new theatres of action. 



Volcanic action has then, ever since the formation of our globe, 

 produced a very elevated temperature, capable of melting the rocks 

 upon which it has exercised its immediate power in all parts of the 

 present continents. One part of this temperature is spread in the 

 interior of the globe in decreasing progression in the direction of the 



» 



center, without our being able to know whether it has already reach- 

 ed the center, in any sensible quantity. The other part is spread to- 

 wards the circumference, also in decreasing progression, and is dissi- 

 pated more or less in the immensity of space. Volcanic operations 

 are at present a remnant, a weak continuation of this great work 

 which still produces unequally disseminated heat, the irregularity of 

 which we might more clearly perceive if it did not take place at so 

 great a depth. 



We may add to this that volcanic explosions frequently eject 

 pyrites which have often formed beds upon layers of existing rogks 

 and which have then been covered with new rocks. These beds 

 of pyrites, continually acted on by the water of the atmosphere 



