However, I remained perfectly still, and presently a little fish
appeared from below. It was soon followed by a second and a third, and
before long a whole shoal of fish were floating almost on the surface,
looking out for insects which had fallen into the water.

The day being hot, and with scarcely a breath of wind, the fish soon
became quite bold. They did not move beyond the small spot in which they
had appeared, but they all had their tails in slight movement, and their
heads in one direction, thus showing that although the water appeared to
be perfectly motionless, there must be a current of some sort, fish
always lying with their heads up the stream, so as to allow the water to
enter their mouths and pass over their gills.

If then these sluggish streams were unlike those of Oxford, where the
ground is low, and nearly level, how utterly distinct must they be from
those of hilly and especially of rocky localities!

In the earlier part of the present year I was cursorily examining a
brook in Cannock Chase, in Staffordshire. Unfortunately, the day was
singularly inauspicious, as the sun was invisible, the atmosphere murky,
and a fierce north-east wind was blowing, a wind which affects animals,
etc., especially the insect races, even more severely than it does man.
Even the birds remain under shelter as long as they can, and not an
insect will show itself. Neither, in consequence, will the fish be "on
the feed."

On a previous visit, we had been more fortunate, trout, crayfish, etc.,
testifying to the prolific character of the brook, which in one place is
only four or five feet in width, and yet, within fifty yards, it has
formed itself into a wide and treacherous marsh, which can only be
crossed by jumping from one tussock of grass to another; and yet, again,
it suddenly spreads out into a broad and shallow torrent, the water
leaping and rippling over the stony bed. Scarcely a bush marks its
course, and within a few yards it is quite invisible.

As we shall presently see, the brooks of the chalk downs of Wiltshire,
and of the regular mixture of rock and level ground, which are
characteristic of Derbyshire, have also their own separate
individualities.

We shall, however, find many allusions to them in the course of the
work, and we will therefore suppose ourselves to be approaching the bank
of any brook that is but little disturbed by man. What will be likely to
happen to us will be told in the following chap