344 GEIKIE 



of crinoids, with foraminifera, corals, bryozoans, brachio* 

 pods, lamellibranchs, gasteropods, fish-teeth, and other un- 

 equivocally marine organisms. It must have been for ages 

 the bottom of a clear sea, over which generation after 

 generation lived and died, until their accumulated remains 

 had gathered into a deep and compact sheet of rock. From 

 the internal evidence of the stratified formations we thus 

 confidently announce a second conclusion that a great 

 portion of the solid land consists of materials which have 

 been laid down on the floor of the sea. 



From these familiar and obvious deductions we may 

 proceed further to inquire under what conditions these 

 marine formations, spreading so widely over the land, were 

 formed. According to a popular belief, shared in perhaps 

 by not a few geologists, land and sea have been continually 

 changing places. It is supposed that while, on the one hand, 

 there is no part of a continent over which sea-waves may 

 not have rolled, so, on the other hand, there is no lonely 

 abyss of the ocean where a wide continent may not have 

 bloomed. That this notion rests upon a mistaken interpreta- 

 tion of the facts may be shown from an examination 

 (i) of the rocks of the land, and (2) of the bottom of the 

 present ocean. 



(i) Among the thickest masses of sedimentary rock 

 those of the ancient palaeozoic systems no features recur 

 more continually than alterations of different sediments, and 

 surfaces of rock covered with well-preserved ripple-marks, 

 trails and burrows of annelides, polygonal and irregular 

 desiccation marks, like the cracks at the bottom of a sun- 

 dried muddy pool. These phenomena unequivocally point 

 to shallow and even littoral waters. They occur from 

 bottom to top of deposits which reach a thickness of several 

 thousand feet. They can be interpreted only in one way, 

 viz., that their deposition began in shallow water; that dur- 

 ing their formation the area of deposit gradually subsided 

 for thousands of feet; yet that the rate of accumulation of 

 sediment kept pace on the whole with this depression; and 

 hence, that the original shallow-water character of the de- 

 posits remained, even after the original sea-bottom had been 

 buried under a vast mass of sedimentary matter. Now, if 



