KNOWLEDGE OF EARTH STRUCTURE 181 



and so also may the shoves upward along the lines of fracture, 

 and crushing may sometimes add to the effect; but elevation 

 from an upward movement of the downward bent crust is only 

 an incidental concomitant, if it occur at all. 



We perceive thus where the truth lies in Professor Le Conte's 

 important principle. It should have in view alone monogenetic 

 mountains and these only at the time of their making. It will 

 then read, plication and shovings along fractures being made 

 more prominent than crushing: 



Plication, shoving along fractures and crushing are the true 

 sources of the elevation that takes place during the making of 

 geosynclinal monogenetic mountains. 



And the statement of Professor Hall may be made right if 

 we recognize the same distinction, and, also, reverse the order 

 and causal relation of the two events, accumulation and sub- 

 sidence ; and so make it read : 



Regions of monogenetic mountains were, previous, and pre- 

 paratory, to the making of the mountains, areas each of a slowly 

 progressing geosynclinal, and, consequently, of thick accumula- 

 tions of sediments. 



The prominence and importance in orography of the moun- 

 tain individualities described above as originating through a 

 geosynclinal make it desirable that they should have a distinc- 

 tive name; and I therefore propose to call a mountain range 

 of this kind a synclinorium, from synclinal and the Greek opos, 

 mountain. 



This brings us to another important distinction in orographic 

 geology that of a second kind of monogenetic mountain. The 

 synclinoria were made through a progressing geosynclinal. 

 Those of the second kind, here referred to, were produced by a 

 progressing geanticlinal. They are simply the upward bendings 

 in the oscillations of the earth's crust the geanticlinal waves, 

 and hardly require a special name. Yet, if one is desired, the 

 term anticlinorium, the correlate of synclinorium, would be 

 appropriate. Many of them have disappeared in the course of 

 the oscillations; and yet, some may have been for a time 

 perhaps millions of years respectable mountains. 



The geosynclinal ranges or synclinoria have experienced in 

 almost all cases, since their completion, true elevation through 

 great geanticlinal movements, but movements that embraced a 

 wider range of crust than that concerned in the preceding geo- 

 synclinal movements, indeed a range of crust that comes strictly 

 under the designation of a polygenetic mass." 



*' The Condition of the Earth's Interior." 



"The condition of the earth's interior is not among the geo- 

 logical results of contraction from cooling. But these results 



