1906. ] 



SEE— THE CAUSE OF EARTHQUAKES, 361 



equalize itself in that direction, and the movement might continue 

 for a long time until subterranean conditions changed. The earth's 

 crust is complex, of unequal thickness in different parts, and broken 

 into un'equal blocks by various faults, which are continually adjust- 

 ing themselves to the strains arising in the underlying substratum 

 supporting them. That some areas should go up while others go 

 down is therefore not at all remarkable ; and most of the oscillations 

 of the land will be found to depend upon causes of this kind. In 

 my opinion the seat of the forces will be found to lie mainly in the 

 fluid substratum beneath. Considering the great number of blocks 

 into which the earth's crust has been shown to be broken by faults 

 such as Professor Suess has so fully discussed for the regions of 

 the Alps and the Tyrol, the oscillations of level with the changes of 

 the strand in salt and fresh water regions seem easily accounted for. 

 In his work on " Meteorics " (lib. I, cap. 12) Aristotle justly 

 remarks : 



" The distribution of land and sea in particular regions does not endure 

 throughout all time, but it becomes sea in those parts where it was land, 

 and again it becomes land where it was sea. . . . 



" And the sea also continually deserts some lands and invades others. 

 The same tracts, therefore, of the Earth are not, some always sea, and others 

 always continents, but everything changes in the course of time." ^ 



§39. Strabo's views on the elevation and depression of the. land. 



In his " Principles of Geology" (pp. 24-25, 12th edition) Lyell 



quotes the views of Strabo regarding the elevation and depression 



of the land as follows : 



" It is not,"' says Strabo, " because the lands covered by seas were orig- 

 inally at different altitudes, that the waters have risen, or subsided, or receded 

 from some parts and inundated others. But the reason is^ that the same 

 land is sometimes raised up and sometimes depressed, and the sea also is 

 simultaneously raised and depressed, so that it either overflows or returns 

 into its own place again. We must, therefore, ascribe the cause to the 

 ground, either to that ground which is under the sea, or to that which be- 

 comes flooded by it, but rather to that which lies beneath the sea, for this 

 is more movable and, on account of its humidity, can be altered with great 

 celerity. It is proper to derive our explanations from things which are 

 obvious, and in some measure of daily occurrence, such as deluges, earth- 

 quakes and volcanic eruptions, and sudden swellings of the land beneath the 

 sea ; for the last raise up the sea also ; and when the land subsides again, they 

 occasion the sea to be let down. And it is not merely the small, but the 



^ Cf. Lyell's " Principles of Geology," 12th edition, Vol. I, pp. 21-22. 



