321] G. E. Dorsey 123 



believe in the deep-sea origin of chalk, and he adds that 

 the organic remains in the chalk were carried there by cur- 

 rents from regions of shallower water. In 1863 Hebert 

 said the chalk of the Paris Basin was formed at a suf- 

 ficiently shallow depth for it to take part in .a period of 

 emergence, being the first hint that chalk might not be 

 abyssal. Delesse was the first to introduce warmth as one of 

 the requisites for chalk deposition, when he said, in 1866, 

 that the water of the Paris Basin was of the same tempera- 

 ture as that of the Gulf Stream today. Then followed in 

 order, W. Thompson, Prestwich, Whitaker, M. J. Murray, all 

 subscribing to the deep-sea origin. In 1877 the first dis- 

 cordant note was sounded by Gwyn-Jeffreys, who declared the 

 molluscs of the chalk were shallow water and tropical forms. 

 A. Geikie, in 1879, supported this idea. Sollas says the 

 sponges indicate a depth of 100-400 fathoms. Lambert, and 

 Prestwich in a later article, Peron, Neumayr, Agassiz, and 

 Jukes-Brown have all held that the chalk was formed in deep 

 waters. But the many indications of emergence that have 

 been found associated with the chalk throughout Europe, and 

 the absence in the main of any organisms that can only be 

 abyssal, have caused most present-day geologists to abandon 

 this idea. A. R. Wallace (15, p. 87, et seq.), in 1880, dis- 

 cusses the origin of chalk as follows: 



" There seems very good reason to believe that few, if any, of the 

 rocks known to the geologists correspond exactly to the deposits now 

 forming at the bottom of our great oceans. The white oceanic mud, 

 or Grlobigerina-ooze, found in all of the great oceans at depths vary- 

 ing from 250 to nearly 3,000 fathoms, and almost constantly in 

 depths under 2,000 fathoms, has, however, been supposed to be an 

 exception, and to correspond exactly to our white and gray chalk. 

 This view has been adopted chiefly on account of the similarity of 

 the minute organisms found to compose a considerable portion of 

 both deposits, more especially the pelagic Foraminifera, of which 

 several species of Globigerina appear to be identical in the chalk and 

 the modern Atlantic mud. . . . Now as some explanation of the 

 origin of chalk had long been desired by geologists, it is not sur- 

 prising that the amount of resemblance shown to exist between it 

 and some kinds of oceanic mud should at once have been seized upon, 



