fresh and important discoveries; and if I am asked for a proof of
what I assert, I point to "Rain and Rivers," written by no professed
scientific man, but by a colonel in the Guards, known to fame only
as one of the most perfect horsemen in the world.

Let me illustrate 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 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