24 
TOPULAB SCIENCE REVIEW. 
THE DEPOSITS OF THE ATLANTIC IN DEEP WATER, 
AND THEIR RELATION TO THE WHITE CHALK 
OF THE CRETACEOUS PERIOD. 
BY PROFESSOR D. T. ANSTED, M.A., F.R.S., For. Sec. G.S., &c. 
[PLATE LV.] 
The origin of chalk, a substance very different from other lime- 
stones with which it agrees nearly enough in chemical com- 
position, has always been a subject of enquiry with geologists, 
and the theories suggested have been numerous and varied. 
It was not till a necessity arose for determining the depth of 
the sea bottom across the Atlantic, preparatory to la} 7 ing the 
cable for the Atlantic telegraph, that deep soundings were sys- 
tematically taken between Europe and America ; but when this 
was done a close relation was detected, both in appearance and 
organic contents, between chalk and the mud dredged up from 
the Atlantic bottom in deep water. Something like evidence 
has thus been obtained as to the possible conditions of deposit 
of the upper member of the cretaceous series. 
White chalk is singularly uniform as a rock in all those parts 
of the world where it has been discovered. It is not always of 
the same degree of hardness, and it occasionally differs in 
colour as well as texture from the white chalk of the south of 
England that may be regarded as the type, but it is everywhere 
a homogeneous fine-grained rock showing few or no marks of 
stratification except on a large scale, and containing in com- 
parison with many other rocks few organic remains of sufficient 
magnitude to be seen by the unassisted eye. It ranges from 
the north of Ireland in the north-west to the Crimea in the 
south-east, a distance of nearly 1,400 miles ; and from the south 
of Sweden in the north almost as far as the Pyrenees in the 
south, a distance of nearly 1,000 miles. In England it ap- 
proaches 1,000 feet in thickness, and in southern Russia it is as 
much as 600 feet. Throughout this wide space it retains 
its essential character as a rock, and cannot readily be mistaken 
