II THE PROBLEMS OF THE DEEP SEA 59 



northern Africa, and western and southern Asia ; 

 and of the gradual diminution of this ocean 

 during the older tertiary epoch, until it is 

 represented at the present day by such teacup- 

 fuls as the CasjDian, the Black Sea, and the 

 Mediterranean; the supposition of Dr. Thomson 

 and Dr. Carpenter that what is now the deep 

 Atlantic, was the deep Atlantic (though merged 

 in a vast easterly extension) in the Cretaceous 

 epoch, and that the Glohigerina mud has been 

 accumulating there from that time to this, seems 

 to me to have a great degree of probability. And 

 I agree with Dr. Wyville Thomson against Sir 

 Charles Lyell (it takes two of us to have any 

 chance against his authority) in demurring to the 

 assertion that " to talk of chalk having been 

 uninterruptedly formed in the Atlantic is as 

 inadmissible in a geographical as in a geological 

 sense." 



If the word " chalk " is to be used as a 

 stratigraphical term and restricted to Glohigerina 

 mud deposited during the Cretaceous epoch, of 

 course it is improper to call the precisely similar 

 mud of more recent date, chalk. If, on the other 

 hand, it is to be used as a mineralogical term, I 

 do not see how the modem and the ancient 

 chalks are to be separated — and, looking at the 

 matter geographically, I see no reason to doubt 

 that a boring rod driven from the surface of the 

 mud which forms the floor of the mid-Atlantic 



