of Ediriburgh, Session 1883-84. 
901 
their cargoes of rocks and rubbish, and at the same time plough 
through the sea bottom, pushing forward boulders, and crushing shell 
fish? (Seep. 891.) 
It is a fact confirmatory of this view, that beds of boulder clay 
never show stratification, and that, moreover, in respect of colour 
and materials, they closely resemble hardened or compressed mud, 
apparently composed of the debris of rocks which had undergone 
disruption and friction by some extraneous agent. Boulder clay 
is found everywhere in Scotland, — so that there must have been one 
general agent instrumental in forming the deposit ; and it is difficult 
to conceive a more probable agent than sea currents, with floating 
ice, grinding and grating over submarine rocks. 
Another circumstance (shown in the Committee’s Eeports) 
indicates oceanic agency, viz., the uniformity all over Scotland of 
the direction of the striae on rocks and boulders, and of the 
direction of the longer axis of boulders. In almost every part of 
Scotland there has manifestly been some agent of immense power, 
which has been for a long period passing over from the W.N.W. 
What other agent would produce these concurrent effects over a con- 
siderable portion of the earth’s surface than a great oceanic current ? 
No such effects are likely to have been produced by an ice- 
sheet however gigantic, or still less by local glaciers. 
The deflections from that normal direction, which are mentioned 
in the Reports as occurring in some localities, are not only not incon- 
sistent with the theory of an oceanic current, but are just what 
might be expected, inasmuch as when currents flow over a bed 
which contains obstructions, eddies and deflections are produced, so 
that these partial deviations from the normal direction strengthen 
rather than weaken the theory of a great sea current. 
There are also two districts crossing Scotland where the movement 
has been, by some special cause, deflected from the normal N.W. 
direction. In the low-level district between the Firths of Clyde and 
Forth, where the highest point is about 150 feet above the sea, the 
direction is about due E. and W. {Abstract, pp. 847 and 872). So 
also in the valley crossing the south of Scotland, the east part of 
which is occupied by the River Tweed and its tributaries, and the 
west part by the Rivers Liddell and Esk, the direction as shown by 
boulders, and by striations on rocks, is from W.S.W. in the western 
