Correspondence. 333 
I am more than ever convinced that the two series of ridges belong to 
one and the same Glacial epoch. The absence of boulders in the valley 
can be explained, I think, in this way, that a glacier partakes very 
much of the character of the ground over which it passes, and really 
the surface part of the island is a cast, so to speak, of the mainland. 
Portions of the ice-sheet were freighted with boulders and parts of it 
were not. In general, of course, the erratics become smaller to the 
south, and this system, for it is a system, of moraines and boulderless 
valleys or depressions, may go far to account for the so-called " fringe." 
The true terminal moraine has yet to be defined. 
Louisville, K\j., March 23, 1891. John Brysox. 
Cretaceous and Tertiary Strata near Wilmington, N. C* Amer- 
ican geological literature contains many references to the Eocene 
beds of Wilmington, N. C. and the Cape Fear river region and to the 
occurrence of Cretaceous fossils in them. This commingling of Cre- 
taceous and Tertiary forms has been denied by some authors and of 
those who accepted the fact some have held that the species were actu- 
ally contemporaneous, others that they were mechanically mixed by the 
breaking down of fossiliferous Cretaceous strata during Eocene time. 
Dr. W. B. Clark who has published! the latest observations on these de- 
posits, gives positive proof of the commingling of faunas and states his 
belief that they were mechanically mixed. 
During a recent visit to that region the writer found the probable 
source of the Cretaceous forms in a bed of highly fossiliferous siliceous 
limestone of Cretaceous age which lies immediately beneath the zone of 
Tertiary phosphatic conglomerate in which the commingling occurs. 
The Tertiary section varies from point to point and is never more than 
a few feet thick. At Castle Haynes, 10 miles north of Wilmington, and 
at Rocky Point, 20 miles north, it may be described as follows: 
1. White limestone with many Tertiary and perhaps a few Cretaceous fos- 
sils 2 to 4 ft. 
2. Conglomerate of greenish phosphatic pebbles, usually cemented with 
lime, in some places imbedded in sandy clay. Sharks' teeth and 
Tertiary molluscs and corals are numerous. Cretaceous fossils also 
occur. Thickness 2 to C ft. 
3. Gray siliceous limestone full of Cretaceous fossils. Thickness undeter- 
mined. 
This last named layer is exposed in the bank of the creek at Castle 
Haynes and a considerable quantity of it has been quarried from be- 
neath the conglomerate in the phosphate pits at the same place. It has 
also been found in the deeper pits at Rocky Point, though at the time of 
my visit it was covered with water. There were many fragments of it 
lying on the dumps there, some of them with the phosphatic conglom- 
erate attached to one side. It is possible that some of the Cretaceous 
species that have been enumerated by various authors as coming from 
the Eocene were really taken from this lowest stratum and mixed on the 
dump, as no previous writer has mentioned the existence of this Creta 
ceous bed though several have stated that the Tertiary rests on the 
greensand marl. 
"Published by permission of the Director of the U. S. Geological Survey. 
tBull. Geol. Soc. Am. Vol. I, pp. 537-539. 
