122 Analysis^ ^c. of Cordier''s Essay upon the 



the (brief) period when history commences," (and when the di- 

 minution in the number of earthquakes at length permitted the 

 earth to be habitable,) " we may count six hundred earthquakes 

 remarkable for violence or extent. The second cause depends 

 upon this, that the permanent diminution of the heat of the earth, 

 no longer produces any sensible contraction in the subterranean 

 regions near to the surface, while its effects still take place in 

 the interior ; either augmenting the distance between the mass- 

 es which have undergone the tirst effects of contraction, or pro- 

 ducing new solutions of continuity in the masses. We may add, 

 that the slow formation of new strata in the interior must be sub- 

 ordinate to the general law, by which liquids contract in bulk on 

 becoming solids. 



" 15. The less flexible portions of the earth's crust, are those 

 nearest the surface ; for the transverse solutions of continuity in 

 them have long ago acquired and lost their maximum of separa- 

 tion. It is evident that the central forces tend to bring nearer 

 too-ether the elementary masses of the surface, in proportion as 

 cooling contracts more and more the bulk of the interior. This 

 process of approach would act uniformly if the layers of the 

 consolidated crust were concentric ; and if all the transverse so- 

 lutions of continuity were found in planes perpendicular to the 

 surface. But it is not so. The state of overthrow of the pri- 

 mordial crust is such, that, considered in its full extent, I can only 

 describe it as a mass of fragments pressing sideways against each 

 other, whose layers are all either vertical or much inclined. Since 

 this state of things took place, the obliquity of solutions of con- 

 tinuity out of number, some of them of prodigious extent, for- 

 bids such an approach of elementary masses as shall be uniform, 

 and proportionate to the central contraction. This approach has 

 been replaced by alterations of level, slight indeed, but sufficient 

 to affect continental surfaces of great extent. Many geological 

 facts agree with this hypothesis. We may take for granted that 

 the effect still subsists, although insensibly. If the secular rise 

 of the basin of the Baltic is constant, it may be explained upon 

 our supposition. In the same way we can account for the change 

 of level in the Mediterranean, which we observed in company 

 with Dolomieu, on the shores of Egypt. (See Description des 

 mines de San (Tanis des anciens) dans le grand ouvrage sur 

 I'Eo-ypte.) According to our notions, all that part of the conti- 

 nent of Africa experiences a depression equal to two or three 

 centimetres every century." 



The other facts of oceanic retrocession collected in the 

 book entitled " Telliamed," and elsewhere, may be account- 

 ed for in the same way. 



