THE EARTH'S INTERNAL HEAT. 15 



age, and with the phenomena of volcanic ac- 



ty. 



This ilieved to be the cooling of the 



earth; by which the shrinkage of the deeper lay- 

 the up; ther, crumpling 



• Ids which a rnately up- 



I and downward. As these shed 



together, the mechanical energy oi coin- 

 ed by the r<»ck material, becomes 

 ng the lines of most intense 



Xhe folds change from 



to a( I time ; for e* ery land i 



k which extend through it in dh 

 tions which wer parallel to 



its shor 



The late Mr. Robert Mallet believe' that the 

 energy of volcanic eruptions was developed by 

 these compressions of the crust Ur also urj 

 that th< ted by the sides of 



an arch of continental land upon its supports 



ild result in crushing the lines itest 



.Ciliated that the temperature 



may be rais illy in this way to a red heat, or 



in to the fusing point of the rocky materials 

 which are crushed. This heat, which is produced 

 locally, he believed to be consumed locally, and to 

 be the - f the explosive energy which ejects 



the materials of which volcam lilt up. 



:e commonly met with in 

 regions undergoing upheaval. 'This is attributed 

 to the underground compression of the rocks 

 which causes upheaval, generating heat. The 



iter near the shore which penetrates to the 

 heated region is raised by that heat to an explo- 

 sive temperature. Volcanos have a linear exten- 



