1D4- /:'. M. Kindle — Stratigraphic Relations of the 



change from yellow-green to a bright emerald-green, and 

 accompanying the change a sudden fall in the quantity of sus- 

 pended matter." Again, he notes the sharply defined limits of 

 the normal Mediterranean waters and the Atlantic current 

 which sets into the Mediterranean : " On the one side of it the 

 water was a vivid green, on the other a deep blue. Standing 

 at the bow of the ship, a bottle could be filled with blue water, 

 while at the same moment a bottle cast from the stern could 

 be filled with green water." It is of course obvious that the 

 amount and kind of sediment which accumulates at any point 

 on the sea bottom will depend largely upon the quantity and 

 kind of suspended matter in the sea water above it. 



The sharp contrasts in the type of deposits which we find at 

 present forming around the coasts of the Gulf of Mexico may 

 be cited here as bearing on the question of the ; ' persistence of 

 lithologic units." Off the mouth of the Mississippi River 

 immense deposits of argillaceous mud are being deposited. 

 The mud brought down by the Mississippi River can not, how- 

 ever, be detected beyond " about 100 miles from the Passes."* 

 A few hundred miles to the eastward of the Mississippi in the 

 Florida-Bahama region we find vast areas of chalky mud. 

 Vaughan'sf work on the Florida coast has shown that the 

 bottom deposits now forming inside the Florida Keys vary 

 from quartz sand to nearly pure calcareous ooze. Thus we 

 find various kinds of deposits are now forming in different 

 parts of the Gulf of Mexico. Tire whole continental platform 

 from Long Island to Hatteras off the east coast of the United 

 States is so swept that, according to Willis,:}: sand alone comes 

 to rest, all finer sediments being carried to deeper waters. 



The systematic examinations of the bottom deposits of the 

 Irish sea have shown that it is characterized by a wide diversity 

 of sediments. Clean sand and mud and clay are prominent 

 among these and have distinct areas of distribution. 



" Clean sand covers the floor generally in the shallow water of 

 the eastern area between the Isle of Man and Lancashire where 

 the depth does not exceed 10 fathoms . . . Mud and clay may be 

 deposited in shallow water under special conditions, but it is 

 principally found in the deep gully lying west of the Isle of Man 

 at depths of 50 fathoms and over."§ 



The bionomic conditions and the character of the bottom 

 deposits of the Black sea as revealed by the researches of 



* Agassiz, A.: Mus. Comp. Zoo!., vol. xiv, p. 128. 



f Vaughan, Thomas Wayland : A contribution to the geological history of 

 the Floridian plateau, Carnegie Institution of Washington, Publication 

 133, p. 119, 1910. 



£ Willis, Bailey: Principles of Paleography, Science, n. s., vol. xxxi, 

 p. 19. 1910. 



£ Herdman, W. A. and Loinas, J. : On the floor deposits of the Irish sea, 

 Proc. Liverpool Geol. Soc, vol. viii, p. 215, 1897. 



