Ill OUR MOLTEN GLOBE 45 



annelides, polygonal and irregular desiccation marks like the cracks 

 at the bottom of a sun-dried muddy pool. These jDhenomena 

 unequivocally point to shallow and even littoral waters. They 

 occur from bottom to top of formations which reach a thickness of 

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

 namely, that the formations in question began to be laid down in 

 shallow water ; that during 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 depres- 

 sion ; and hence that the original shallow-water character of the 

 deposits remained after the original sea-bottom had been buried 

 under a vast mass of sedimentary matter." 



Coming now to the other end of the geological record, 

 we find in the deltas of existing rivers an exactly similar 

 phenomenon. At Venice a boring of 400 feet deep was 

 entirely in modern fluviatile mud, the bottom of which 

 was not reached ; and at four separate depths, one of them 

 near the bottom, beds of turf or of vegetable matter were 

 passed through, showing, as Sir Charles Lyell observes, 

 " that a considerable area of what was once land has sunk 

 down 400 feet in the course of ages." ^ At Zagazig, on the 

 eastern border of the Nile delta, borings have been made 

 for the Royal Society, and have not found rock at a depth 

 of 345 feet. In the delta of the Mississippi a well at New 

 Orleans, 630 feet deep, passed entirely through sands and 

 clays, with fresh-water shells of living species. Again, in 

 the delta of the Ganges, at Calcutta, a boring 481 feet deep 

 was entirely through beds of sand, peat, gravel, and other 

 alluvial or fresh-water deposits. This remarkable concur- 

 rence of testimony from so many parts of the world and 

 from different geological periods, indicates a general law 

 of subsidence so uniformly coinciding with deposition, and 

 so regularly keeping pace with it, that we can hardly avoid 

 the conclusion that the two phenomena are connected; 

 and the most reasonable explanation seems to be that the 

 deposit of matter in a shallow sea directly causes the de- 

 pression of that bottom by its weight. Such depression is 

 quite intelligible on the theory of a thin crust resting or 

 .floating on a liquid substratum, but is quite unintelligible 

 on the supposition of a solid globe, or of a crust several 



^ Friiiciphs of Gtolo(jy, 11th ed., vol. i., p. 422. 



