46 CARNEGIE INSTITUTION 



ties is such that the condition called by Fourier ' •' the steady flow 

 of heat," would subsist. In such a globe cooling would be ac- 

 companied by no superficial deformation. It is therefore essential 

 to the solution of the problem that the character of such an ideal, 

 undeformed sphere should be worked out from the mathematical 

 side. If it can be shown that the constitution of the earth does not 

 conincide with that cf this hypothetical globe, a reason for defor- 

 mation will have been discovered. As soon as an approximate so- 

 lution has been attained for the constituent materials of the globe 

 and their properties, then comparison v/ith the hypothetical sphere 

 of no deformation will show the general character cf the deforma- 

 tion which should be expected in the earth. 



It appears possible that some of the greater phenomena wnich 

 must be discussed under the head of upheaval and subsidence are 

 not connected with the cooling of the globe, but with the retarda- 

 tion of its rotation and the consequent changes in its form in main- 

 taining equilibrium. It is a very remarkable fact, not recorded in 

 literature, so far as I know, that most of the great continental out- 

 lines lie approximately on great circles which are nearly tangent 

 to the Antarctic Continent and the Arctic Ocean. It seems possible 

 that these great coast lines answer to the directions of rupture of a 

 spheroid retarded by tidal action. A proper discussion of the mat- 

 ter requires a knowledge of the constituents of the earth and of the 

 laws of rupture, which are as yet in a most unsatisfactory con- 

 dition. 



Orogenic d5^namics is a mere branch of upheaval and subsidence 

 involving the theory of elasticity, plasticit3^ and rupture for finite 

 strains. It must explain the origin of joints, systems of veins, 

 slaty or schistose cleavage and the simpler flexures. 



It is evident, then, that the problem of upheaval and subsidence 

 is linked by the closest ties to the problem of the earth's constitu- 

 tion and should be conducted by the same corps of physicists. 



Our knowledge of the operative causes in vulcanism is of the 

 vaguest description. It seems almost certain, however, that these 

 impressive thermal phenomena cannot be wholly independent of 

 the vast amount of energy dissipated in the orogenic upheavals 

 which so often accompany eruptivity, The thermodjaiamic side of 

 this problem therefore demands earnest study. 



Vulcanism also raises other and very difficult questions. That 

 magmas are soUttions is known, l)ut scarcely anything else is 

 known about them. Thus, vulcanism implies researches on the 



