536 S. V. Wood,jun. — American and British Sur/ace ■ Geolog]). 
comparison it is noticeable that tbe sonndings obtained from this 
area also resemble tbe rock under examination in tbe comparative 
rarity of Pulvinulina Micheliniana, one of tbe commonest of Atlantic 
Foraminifera, and in tbe scarcity of tbe arenaceous types. But little 
care was taken, in the process of washing, to preserve the Radiolaria, 
but such as remain are of tbe same species as tbose of tbe line of 
dredgings alluded to. 
In conclusion, it appears to me not too mucb to say that after 
disintegration and washing this “Chalk” from tbe New Britain 
Group could not possibly be distinguished by its organic remains 
from a washed Globigerina-ooze dredged in 1500 to 2500 fathoms 
in the South Pacific. The determination of the exact geological age 
is a matter for geologists ; my observations have necessarily been 
limited to the pbysical characters and the organic constituents of 
the specimen placed in my hands by Prof. Liversidge, but it appears 
worth considering whether the rock may not be part of a recent sea- 
bottorn which has been distributed by volcanic or other agency. 
Such deposits may be very old chronologically speaking, and we 
know by dredging experience that they do often become very hard 
and compact even comparatively near the shore. Mr. Brown’s letter, 
quoted above, provides us witb the required disintegrating force. 
III. — American “ Surface Geology,” and its Relation to British. 
With some Remarks on the Glacial Conditions in Britain, 
ESPECIALLY IN REFERENCE TO THE “ GREAT IcE AGE ” OF Mr. 
James Geikie. 
By Searles V. "Wood, Jun., F.G.S. 
(PART II.) 
( Continued from page 490.) 
N UMEROUS buried channels filled with drift occur over Ohio and 
the neighbouring States forming the St. Lawrence basin. Some 
of these penetrate the water-parting, and formed, according to Prof. 
Newberry, waste weirs through which the lake waters of the St. 
Lawrence basin escaped into the valley of the Mississippi, as the 
land rose and the sea retired from that valley. This, if I understand 
him rightly, took place after the beds 3a had been formed, and 
before the terraces, to be described under the number 4, began to 
form by the fall of the lake waters ; but these waste weirs would 
seem to have probably acted the same part also at an earlier period, 
viz. during the commencement of the Erie clay deposit, when the 
lake began to form by the recession of the ice from the water-parting, 
and when it must have been full up to the brim of that parting, or 
at least up to the level of the waste weirs. 
The final shrinking, however, of the waters of the lake-basin is 
marked, according to Prof. Newberry, by the formation of clearly- 
marked terraces or lake-beaches at successive levels, the uppermost 
of which inosculates with these waste weirs. The shrinkage giving 
rise to thern may have arisen, he says, from the removal of ice-dams 
