British Drift Theories. — Upham. 27 i 
1892; and the second describing and explaining the analogous 
rubble drift in the Mediterranean region of southern Europe 
and northern Africa, forming pages 903-984 in vol. clxxxiv, 
for 1893, of the Philosophical Transactions of the Royal So- 
ciety of London. Similar conclusions, drawn from less ex- 
tended investigations, had been published by Prof. Prestwich 
in 1875 and 1880. 
Although the rubble drift in southern England and Wales 
is ascribed by Prestwich to a marine submergence of 900 or 
perhaps 1,000 feet, the only fossils found in the formation are 
those of land shells and land animals, and no shore line nor 
terrace of marine erosion or beach deposition has been detect- 
ed, such as would mark the limits or stages in the oncoming 
or decline of the submergence. Prof. Prestwich thinks that 
the effects observed indicate simply currents of the sea flow- 
ing down from the hillsides while the land was suddenly ris- 
ing, rather than that the rubble transportation was due t<» 
waves of earthquake origin. It is very difficult, however, at 
least for me, to see how such currents, even with estuarine 
tidal action, could have produced the observed results, for, the 
total rise being only about 1,000 feet, it would hardly have 
more effect than the flow of a powerful river current upon its 
banks during the few minutes in which the Mow would ad- 
vance 1,000 feet. If the emergence were at the rate of the 
fall of tides, as one or two feet in an hour, 25 or 50 feet in a 
day, and the whole amount of 1,000 feet in a month, requiring 
longer time if subdivided by intervals of rest, it would be 
quite inadequate to form the rubble drift. But so sudden, 
and not seismic, uplifting of extensive areas as this supposed 
by Prestwich for western and southern Europe, and in Amer- 
ica b} T Shaler for the coastal border of New England,* seem- 
to be physically impossible. 
It seems to me, on the contrary, farmore probable thai tin- 
true explanation of (lie origin of the rubble drift is supplied 
by the second of the previously proposed hypotheses concern- 
ing it. which Prestwich states but rejects, namely, "the agency 
of ice and snow sliding down the hill-slopes, aided by the run- 
ning off Of the water resulting from the melting of the ice 
• :: i'. s. Geological Survev. Seventh An. Rep. for 1885-80, pp. :;!<•. 320, 
321; Bulletin No. •">:. 18S9,*"The (xeolojn of Nantucket," pp. 14, r>. 
