12 Proceedings of the Royal Physical Society. 
Chalk observed in the United States, as in the neighbourhood 
of Kansas City.” 
I am not going to enter into the much-vexed question as to 
the conditions under which the White Chalk was laid down, 
or the probable depth of the Cretaceous Mediterranean above 
referred to. It is well known that some high authorities 
regard the Chalk as essentially and strictly a shallow-water 
formation, while others have maintained its deep-water 
origin. It seems highly probable that neither of these 
extreme views is correct. It is tolerably certain that in 
some regions the Chalk was deposited near a shore-line, while 
in others it was laid down in water which may fairly be 
called “deep,” though not strictly “abyssal” in depth. Dr 
W. Fraser Hume, who has carried out an elaborate research 
into the constitution of the Chalk, with a special view to the 
solution of this problem (Joc. cit., supra, and Chemical and 
Micro-Mineralogical Researches on the Upper Cretaceous 
Zones of the South of England, 1893), comes to the general 
conclusion that “such evidence as is forthcoming from faunal 
considerations” would point to the deposition of the Chalk in 
“an ocean which, if not abysmal, at least possessed depths 
far exceeding those of many very prominent marine areas.” 
He points out that while we have in such regions as France 
and Saxony clear evidence that the Upper Cretaceous rocks 
are of the nature of shallow-water deposits laid down near 
a shore-line, in other regions, as in Russia, the Chalk is 
essentially calcareous, and has a thickness of sometimes over 
1800 feet, thus indicating very considerable depths of water. 
Hence he concludes that the Cretaceous Mediterranean may, 
like the present sea of that name, have possessed in places 
depths of 1000 fathoms or more. 
Another strikingillustration of great changes of relative posi- 
tion in the dry land and sea within geologically recent times 
is afforded by the Nummulitic Seriesof the Eocene period. This 
series, as is well known, is essentially calcareous, and, where 
fully developed, consists of several thousands of feet of mas- 
sive limestones of undoubted marine origin. The Nummulitic 
ocean not only occupied the site of the present Mediterranean, 
and covered the lands immediately contiguous to this, both 
