lbtjy.J THE DISPLACEMENT OF BEACH-LINES. 79 



disturbances in the solid earth, were it not for the fact that 

 great strains are accumulated by other forces, and that the 

 earth is in many places strained to the very limit of elasticity. 

 In such very weak places an inconsiderable force may be suffi- 

 cient to release the strain, and we may in this manner under- 

 stand, that even a change of barometric pressure might per- 

 haps be sufficient to give rise to earthquakes. 



We will now investigate, whether the displacements of the 

 beach-lines which took place in the Tertiary and Quaternary 

 times were so considerable, that they cannot be explained by 

 the aid of our hypothesis. 



It is only in the folded chains, that Tertiary marine forma- 

 tions have been lifted to very considerable heights above the 

 sea. But the folding is a local phenomenon. The folded chains 

 of Cainozoic age are few, and compared with the total surface 

 of the globe they are of very small extent. If two great divi- 

 sions of the crust which are separated by a line of weakness, 

 move in different directions at the same time or in the same 

 direction at different times, great quantities of eruptive matter 

 may be squeezed out at the line of weakness, and great local 

 foldings may be caused at the same line by the different move- 

 ments on either side; nay, even in lower latitudes, where, 

 according to the hypothesis, all is sinking, great mountain chains 

 may be elevated at such lines of weakness. In considering 

 1 e highest and youngest mountain chains of our earth, we 

 see that their site agrees pretty well with the hypothesis. 



e ranges bordering the Pacific run along the division between 

 ercat continents and a deep ocean. It is, as shown above, 

 Probable that the effect of the decreasing centrifugal force is 

 finished by the movements of the sea, which immediately ac" 

 commodates itself to the change in the length of the day, and 

 at ' from this cause, sea-bottom and land will not move con- 

 temporaneously. A nd the great chains which run acrosss Eurasia, 

 J°m the Himalayas to the Pyrenees and the Atlas mountains, were 



anVth ed at - the b ° rder ° f the great Tertiary Mediterranean sea» 

 e y He in latitudes about the situation where we would expect 



