1889.] 



THE DISPLACEMENT OP BEACH-LINES. 



19 



that the force has not acted sufficiently long. The effect of the 

 force is therefore dependent on time, when it has to overcome 

 a considerable resistance. „Upon tension", Schiotz states (Laere- 

 bog i Fysik. Chria. 1881 p. 65) „the elongation steadily increases, 

 although quite slowly after it has once begun; therefore a load, 

 that acting only for a short time would not produce any elon- 

 gation, may perfectly well do so if permitted to act for a longer 

 period. This is the case in general, and is not confined to elon- 

 gation only; from this cause do metal springs lose their resili- 

 ence with time, and beams become curved little by little. Upon 

 long continued application a wire breaks under a less strain than 

 it does on a short application." 



It appears to me, that there is here a force which must be 

 able to cause disturbances in the solid earth. I think that this is 

 „the unknown force from the deep", which has upheaved the 

 mountains of western North America, and which Dutton refers 

 to. The sidereal day lengthens very slowly. The sea follows 

 the slightest alteration in the length of the day and slowly 

 rises in higher latitudes. But the solid crust opposes a resistance 

 to change of form, and first begins to yield when the strain has 

 attained a certain point. When that point is reached, the crust 

 also begins to be upheaved in higher latitudes. 



In the lower latitudes these movements occur in the reverse 

 direction. The solid crust is probably more sluggish than the sea 

 in its movements, and whilst the sea moves itself evenly and 

 uninterruptedly, probably the change of form in the solid crust 

 may take place more in paroxysms, with intermediate pauses in 

 which fresh straining forces collect themselves for renewed action. 



„The elevation of mountains", A. Geihie states, (Textbook of 

 Geology. London 1882 p. 917) „is, in most cases, due to a long 

 succession of such movements" and (L c. p. 919) „the' elevation 

 of mountains like that of continents has been occasional and so 

 to speak paroxysmal." The disturbances in the crust take place 

 along the same fissures repeatedly (vide, for instance, Brogger: 

 Bildungsgeschichte des Christianiafjords, Separataftryk. Chria. 

 1886 p. 78). Something similar takes place on volcanic eruption. 



