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 find 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 conclusions; 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 remains in them, even after
they are civilised, and all other forms of the dread of Nature have
died out in them, a dread of size, of vast space, of vast time; that
latter, mind, being always imagined as space, as we confess when we
speak instinctively of a space of time. They will not understand
that size is merely a relative, not an absolute term; that if we
were a thousand times larger than we are, the universe would be a
thousand times smaller than it is