e my meaning by an example. A man--I do not say a
geologist, but simply a man, squire or ploughman--sees a small valley,
say one of the side-glens which open into the larger valleys in the
Windsor forest district. He wishes to ascertain its age.

He has, at first sight, a very simple measure--that of denudation. He
sees that the glen is now being eaten out by a little stream, the product
of innumerable springs which arise along its sides, and which are fed
entirely by the rain on the moors above. He finds, on observation, that
this stream brings down some ten cubic yards of sand and gravel, on an
average, every year. The actual quantity of earth which has been removed
to make the glen may be several million cubic yards. Here is an easy sum
in arithmetic. At the rate of ten cubic yards a year, the stream has
taken several hundred thousand years to make the glen.

You will observe that this result is obtained by mere common sense. He
has a right to assume that the stream originally began the glen, because
he finds it in the act of enlarging it; just as much right as he has to
assume, if he finds a hole in his pocket, and his last coin in the act of
falling through it, that the rest of his money has fallen through the
same hole. It is a sufficient cause, and the simplest. A number of
observations as to the present rate of denudation, and a sum which any
railroad contractor can do in his head, to determine the solid contents
of the valley, are all that are needed. The method is that of science:
but it is also that of simple common sense. You will remember,
therefore, that this is no mere theory or hypothesis, but a pretty fair
and simple conclusion from palpable facts; that the probability lies with
the belief that the glen is some hundreds of thousands of years old; that
it is not the observer's business to prove it further, but other persons'
to disprove it, if they can.

But does the matter end here? No. And, for certain reasons, it is good
that it should not end here.

The observer, if he be a cautious man, begins to see if he can disprove
his own conclusion; moreover, being human, he is probably somewhat awed,
if not appalled, by his own conclusion. Hundreds of thousands of years
spent in making that little glen! Common sense would say that the longer
it took to make, the less wonder there was in its being made at last: but
the instinctive human feeling is the opposite. There is in men, and
there re