the Displacement of Shore-lines, 400 



ceivable that under high latitudes the sea-level rises and sinks 

 with the eccentricity of the earth's orbit. 



Great part of the earth's surface consists of strata which 

 still lie undisturbed in their original horizontal position. 

 These parts are called " tables " by Suess. But in many 

 places the crust of the earth is so traversed by clefts and 

 fissures that it may be compared to a breccia. Fragments 

 are often displaced relatively by thousands of feet. Strata 

 which originally lay horizontally are folded, thicknesses of 

 7000-8000 feet are bent as if they were straws (Kjerulf, 

 Udsigt over Norges Geologi, 1879, p. 76). Moreover, the 

 folded strata are upheaved far above their original level. 

 Even marine formations so recent as the Eocene are uplifted 

 to heights of 21,000 feet above the sea (Suess, Antlitz der ^ 

 Erde, i. p. 564). Sometimes they stand vertically ,~or are in- 

 verted, so that older strata cover the younger ones. Through 

 fissures eruptive masses are brought forth, and have covered 

 thousands upon thousands of square kilometres. The dis- 

 tribution of land and sea also varies. It is indeed supposed 

 that the great depths of the ocean and the great continents 

 have essentially retained their original distribution from the 

 most ancient times, but the shore-lines wander periodically to 

 and fro ; and these changes of the earth's surface have taken 

 place from earliest times, and are still in action at the present 

 day. 



Geologists in general seek the explanation of these phe- 

 nomena in the cooling and contraction of the body of the 

 earth. The earth's crust folds, just as the skin of an apple 

 wrinkles as the apple dries. The leading geologists of the 

 present day adopt this theory, and A. Geikie in his * Text-book 

 of Geology' (London, 1882, p. 287) says with perfect justice : — 

 " With modifications, the main cause of terrestrial move- 

 ments is still sought in secular contraction." 



According to this doctrine changes in the crust of the 

 earth are due to the interior contracting more strongly than 

 " the crust," so that the latter is too large for it. Its weight 

 drags it down. By this means great horizontally acting 

 pressure is produced in the crust, which must then become 

 folded and cracked in places. The fragments sink down. 

 By this means are formed what Suess has called " Einbriiche." 

 When a part of the crust remains in position while all around 

 it sinks, there is produced what Suess has called a " Horst." 

 The old theory of forces acting vertically from below is most 

 decidedly rejected by Suess. He and Heim have shown, by 

 their investigations of the Alps, that the foldings of the Alps 



