Tae ee 
145 
At the Washington meeting in 1844 he read a paper on 
the Berkshire trains, discovered by Dr. Reid. All that he 
knew of the Drift he had published the year before in his 
annual State Geological Report. This was a special and 
remarkable case. It has never been elucidated. Dr. 
Hitchcock describes the phenomenon, but leaves it unex- 
plained. His conclusions are all merely negative, and 
exhibit, in a striking manner, the cautiousness and fidelity 
of his scientific methods. Ist. The blocks of the trains 
must have been scattered during the latter part of the drift 
period, and by the drift agent, whatever that was. 2d. It is 
impossible to explain the case by any merely aqueous theory 
of drift. 3d. It is equally impossible to explain it by ice- 
bergs; or, 4th, by river pack ice; or, 5th, by the medial 
moraine of a glacier ; or, 6th, by reference to the unexplained 
patches of angular fragments on the Falkland Islands, de- 
scribed by Darwin. “In short,” he concludes, “ I find so 
many difficulties on any supposition which I can make, that 
I prefer to leave the case unexplained until more analogous 
facts have been observed.” 
At the meeting of the British Association at Edinburgh, 
in 1850, he read a paper upon his favorite subject, the ter- 
races of the drift period, after he had made a visit to 
Wales, where he at once recognized the marks of the former 
existence of glaciers up to a certain height, above which he 
recognized the marks of mere drift agency, and to Switzer- 
Agassiz had taught respecting th 
grand glaciers of the Al But his Massachusetts expe- 
riences had so preposessed him with notions of modified drift, 
that he thought he could see how the moraine matter of 
the plain of Switzerland had been subsequently thrown into 
te He was therefore prepared, on his return to Eng- 
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