CHAP. VI GEOGRAPHICAL AND GEOLOGICAL CHANGES 85 



So far from this being a " mathematical demonstration," 

 it appears to me to be a complete misinterpretation of 

 the facts. Animals did not create the lime which they 

 secrete from the sea-water, and therefore we have every 

 reason to believe that the inorganic sources which origin- 

 ally supplied it still keep up that supply, though perhaps 

 in diminished quantity. Again, the great lime-secreters — 

 corals — work m water of moderate depth, that is, near 

 land, while there is no proof whatever that there is any 

 considerable accumulation of limestone at the bottom of 

 the deep ocean. On the contrary, the fact ascertained by 

 the Challenger, that beyond a certain depth the 

 " calcareous " ooze ceases, and is replaced by red and grey 

 clays, although the calcareous organisms still abound in 

 the surface waters of the ocean, shows that the lime is 

 dissolved again by the excess of carbonic acid usually found 

 at great depths, and its accumulation thus prevented. As 

 to the increase of limestones in recent as compared with 

 older formations, it may be readily explained by two 

 considerations : in the first place, the growth and develop- 

 ment of the land in longer and more complex shore lines 

 and the increase of sedimentary over volcanic formations 

 may have offered more stations favourable to the growth 

 of coral ; while the solubility of limestone in rain-water 

 renders the destruction of such rocks more rapid than that 

 of sandstones and shales, and would thus, by supplying 

 more calcareous matter in solution for secretion by lime- 

 stone-forming organisms, lead to their comparative 

 abundance in later as compared with earlier formations. 



However weak we may consider the above-quoted argu- 

 ments against the permanence of oceans, the fact that 

 these arguments are so confidently and authoritatively put 

 forward, renders it advisable to show how many and what 

 weighty considerations can be adduced to justify the 

 opposite belief, which is now rapidly gaining ground among 

 students of earth-history. 



Shore Deposits and Stratified Rocks. — If we go round the 

 shores of any of our continents we shall almost always find a 

 considerable belt of shallow water, meaning thereby water 

 from 100 to 150 fathoms deep. The distance from the 



