150 YVATKORLSE CAPHOLOGY. 
Such are examples of the old-world stories disclosed by every rocky 
shore, railway-cutting, and river-cliff. We have been describing not what 
might have been, but what was; for we can prove every assertion, seeing 
that the rocks themselves furnish incontrovertible data. 
Reasoning regarding Surface Phenomena. 
1. Iceberg Action.—In some parts of Britain, as in the central region of 
Scotland, there are exhibited certain remarkable appearances from which 
striking deductions may be drawn. We find that all the hills, eminences, 
and rocks are precipitous towards the west, and exhibit traces of being 
rendered so by a mighty force wearing them down on that side. In the 
level ground between these heights we find a thick deposit of fine blue 
tenacious clay, with embedded stones, rounded and water-worn, which is 
known as boulder-clay. Also, laid down here and there, sometimes on 
mountain tops, we find enormous blocks brought from great distances to 
the west, as shewn by the rock of which they are made. We also dis- 
cover all across the country certain remarkable scratchings, and deep 
indentations on the exposed surfaces of the hardest rocks, all pointing 
in one direction, at right angles to the broken cliffs. We also note that 
all heights are rounded and worn, as if ground down by some powerful 
agent moving over them. 
The problem before us therefore is—How are all these appearances to 
be accounted for, and by what agent or agents were they produced ? 
It is evident, from the existence of the clay, that the whole region 
referred to must have lain under water. But water alone, even in a 
powerful current, could not carry the blocks, and make the deep scratches — 
that everywhere are seen. It is evident that these effects must have been 
- produced by something borne on the surface of the water, of size and 
hardness capable of doing all this. What hard substance, therefore, can 
_be borne by water, that can carry rocks and leave deep scratchings behind 
it? Nothing but ice in the form of huge bergs; and a current bearing 
packs of these on its surface fully satisfies all the requirements of the 
case. Floating along, of enormous size, these ice-mountains wear down all 
surfaces over which they move; carry from great distances, and drop as 
they melt, blocks of every size ; dash against and wear down into cliffs all 
opposing eminences ; and leave marks on the rock-surfaces identical in 
appearance with those everywhere exhibited ; while the current that bears 
them along, deposits in the lower grounds the mud and boulder débris 
they generate in their onward course. Thus we prove incontestibly that 
icebergs floated over the district exhibiting these phenomena. But was 
the climate such as to generate icebergs? This is proved, independently 
of the above reasoning, by various considerations ; amongst others, by the 
fact, that in the boulder clay in various parts shells are found, called boreal 
