260 Proceedings of the Royal Society 
steep bank or cliff wbich pretty generally along onr coasts rises 
from a flat elevated about 40 feet above the sea, has always been 
spoken of as a beach formed by the sea, and not a few calculations 
have been made to determine from a comparison with our existing 
sea-beach the length of time during which the sea must have stood 
at the higher level, in order to its having eroded our land in the 
very marked way which the upper or 40-foot terrace presents. 
But plainly, before any such calculations are legitimate, it ought 
to be proved that the 40-foot terrace is really the work of the sea. 
Now, this seems to have been somewhat hastily assumed. Unde- 
niably, the sea does act powerfully on the shore, cutting out a step 
or forming a beach line along its margin ; further, it is obvious, 
that that margin was at one time 40 feet higher along our coasts 
than now, and the inference has been jumped at, that the terrace 
which does certainly exist at that level was formed by the sea. In 
other words, a connection of proximity between the sea and the 
40-foot terrace being proved, the connection of cause and effect has 
been assumed. But is the assumption legitimate ? Now this cutting 
at Port-Grlasgow shows that the 40-foot terrace exists not merely 
on the external surface, but in the rock beneath. The superficial 
deposits are merely the clothing of a rocky skeleton beneath, and 
the terrace which we can trace on the surface, we find existing in 
the rock below. What then gave its form to that rocky skeleton 
below? Was the sea the agent which cut the terrace there? 
Plainly not, for when the sea beat on the shore 40 feet above its 
present level, the rock, in its present form, was buried even deeper 
than now under that mass of boulder-clay which still covers it, and 
which the sea, at this particular spot at least, and at many others, 
was not able to penetrate. But was the boulder-clay already there ? 
Admitting what is obvious, that if there, it alone and not the un- 
derlying rock could be fashioned by the sea, are we sure that it 
really was already deposited, or may it not rather have been depo- 
sited at the very time we are speaking of, when the land in its up- 
ward progress still stood 40 feet lower than now ? 
Now, of this earlier presence of the boulder-clay we have abundant 
proof. The rock surface here and elsewhere on our coasts is sharply 
striated. The striating agent, it is now generally admitted, was 
land ice in the form of a thick glacier cake, grinding downwards, 
