1 6 Dwellers of the Sea and Shore 



present a cooling mass. Now a cooling body contracts, 

 and as it does so it has a tendency to warp. Particu- 

 larly does this become evident in the case of our globe. 

 Although its rock-ribbeci surface is seemingly solid, 

 nevertheless, it is endowed with great plasticity, and 

 consequently the shrinking shell results in rumpled 

 ridges and rugosities. Time and the elements have 

 done much in the past to obliterate these folds and 

 wrinkles, but they are still manifest in what is left of 

 the mountain ranges and in the abyssal valleys of 

 the sea. 



In many regions in the world the contracting crust 

 is causing certain portions of continents slowly to rise 

 while at the same time, but in another place, it is 

 causing the land to lower. In the latter event the sea 

 hastens the disappearance. Where an elevation is 

 taking place, however, it sometimes progresses more 

 rapidly than the waves can work. Notwithstanding, 

 to some extent the sea is always cutting away our 

 shores. 



There is enough water In the sea easily to cover the 

 entire earth, provided the earth were a perfectly 

 smooth sphere — that is, if all the mountains and valleys 

 of the land and sea were brought to a common level. 

 But that the earth was ever completely inundated at 

 one time seems unlikely, for it appears that the more 

 solid part has always been too unstable. Now a por- 

 tion is up, then it is down. This seesawing, this oscil- 

 lating of the land, has continued throughout so many 

 ages and in so many places that to-day there is no con- 

 tinent or part of a continent which has not at some time 

 been at the bottom of the ocean. What is more, it is 



