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92 A. C. RAMSAY ON THE PHYSICAL HISTORY
river, just as the streams that issue from the smaller glaciers of
to-day attack the terminal moraines and restrict their growth.
A necessary consequence of the powerful flow of such a large
body of glacier- water must have been to carry the waterworn stones
onward to Basel and into the flats beyond; and in time, as the river
changed its channel and wandered hither and thither across the
plain, the gravels got scattered over the whole of its area. The
thick strata of sand, loam, and gravel that form the present plain of
the Rhine are therefore in great part the waterworn debris of old
moraines, just as the gravels of the plains of Piedmont and Lom-
bardy are relics of the moraines of the gigantic glaciers of the
Italian side of the Alps. This view of the origin of the gravels of
the Rhine was pointed out to me thirteen years ago by Professor
Desor, of Neuchatel, though I do not recollect that he has printed
any thing on the subject.
The substance of the foregoing remarks may be summed up as
follows

—

1. During portions of the Miocene epoch the drainage through
part of the valley that lies between the Schwarzwald and the Vosges
was in great part from north to south, or, in other words, from the
hills north of Mainz into the area now occupied by the Miocene rocks
of Switzerland.
2. After those physical disturbances and elevations that closed
the so-called Miocene epoch in these regions, the direction of the
drainage was reversed, and thus it happened that

—
3. After passing through the hill-country between the lake of
Constance and the place where Basel now stands, the Rhine flowed
along an elevated plain formed of Miocene rocks, the relics of which
still exist between Basel and Mainz.
4. At the same time the Rhine flowed in a minor valley through
the upland country formed of the Devonian rocks that now con-
stitute the Taunus, the Hundsruck, and the contiguous high land
lying northerly towards Bonn.
5. Then by the ordinary erosive action of the great river the gorge
was gradually formed and deepened to its present level, and —
6. Just in proportion as the gorge deepened, so the gently inclined
Miocene strata of the area between Mainz and Basel were also in
great part worn away, so as to leave the existing plain, which to
the uninstructed eye presents the deceptive appearance of once
having been occupied by a great lake*.

Since this memoir was sent to the Geological Society I have read a learned
paper sent to me by Professor Fridolin Sandberger " On the Upper Ehine
Valley in Tertiary and Diluvial Times " (Das Ausland, No. 50, Dec. 15, 1873).
This memoir, which is of the highest value, contains a great amount of infor-
mation on the relations, stratigraphical and palfeontological, of all the formations
found in the valley of the Ehine from the Upper Bunter Sandstone down to
the times of the Loess and superficial gravels.
Professor Sandberger only here and there incidentally touches upon the physi-
cal questions to which I confine myself, and apparently had no intention of
going into the details by means of which I attempt to prove what I conceive to be
the physical history of the valley, especially in its later stages. Wherever he
does touch on these subjects, however, there is no discrepancy in our views.