Glacial Epoch in North America. 573 
2. 4 On a Deep Channel of Drift at Hitchin (Hertfordshire).' 
By William Hill, F.G.S. 
Evidence is given, from nine borings running along a line slightly 
west of north from Langley through Hitchin, of the existence of a 
channel of considerable depth, now filled with Drift, occupying the 
centre of an old valley in the Chalk-escarpment, which may be 
called the Hitchin Y alley. For the first 3 miles it appears to 
be contained within narrow limits, persistent ridges of Chalk 
occurring on each side, and it might almost be compared to a 
Chalk-combe. At Hitchin, after passing between two Chalk- 
knolls, its confines become less clear, and there seems to be some 
evidence of broadening as it emerges on to the Lower Chalk-plain 
and leaves the higher ground of the main Chalk-escarpment. - The 
greatest depth to which the channel has been proved is at a boring 
in Hitchin, where the Gault was reached beneath Drift at a depth 
of 68 feet below sea-level. That the channel flowed northwards 
and belonged to a ' subsequent ' stream seems to be proved by the 
fact that at Braybury End, the only place where a southerly stream 
could pass, the space between bare Chalk-exposures is but 450 yards. 
and in about the middle of the space Chalk has been reached within 
50 feet of the surface (that is, about 200 feet above sea-level) in a 
well dug a few years back. The channel must be older than the 
Chalky Boulder-Clay, which still partly fills it as far south as Langley, 
and may have blocked it to the southward and given rise to the 
features now presented in the drainage on the northern slope of 
the escarpment. But the author is inclined to suggest that either 
glacier-ice or bay-ice must have played no unimportant part in 
damming up the old valley. The author suggests the existence 
of another channel, in this case draining southwards, buried under 
the broad area of Boulder-Clay and gravel which lies immediately 
south of Stevenage and to the north as far as Letchworth and 
Wilbury Hill. But a narrow space of bare Chalk, at an elevation 
of 240 feet O.D. connecting large areas east and west of it, pre- 
cludes the occurrence of a channel farther north than Letchworth. 
January 8th, 1908.— Sir Archibald Geikie, K.C.B., D.C.L., Sc.D., 
Sec.R.S., President, in the Chair. 
The following communications were read : — 
1. 'Chronology of the Glacial Epoch in Xorth America.' By 
Prof. George Frederick Wright, F.G.S. A. 
In the case of Plum Creek, Lorain County (Ohio), the study of the 
activity of the stream and of the amount of work which it has done 
since a certain stage of the Glacial Epoch, has yielded important 
results. This stream began the erosion of its trough when the 
temporary lake, held up in front of the ice, was maintained for a 
considerable period at the level of its Fort-Wayne outlet ; it has 
Phil. Mag. S. 6. Vol. 15. No. 88. April 1908. 2 Q 
