Books about angling should be divided (according to De Quincey's
method) into two classes,--the literature of knowledge, and the
literature of power.

The first class contains the handbooks on rods and tackle, the
directions how to angle for different kinds of fish, and the guides
to various fishing-resorts.  The weakness of these books is that
they soon fall out of date, as the manufacture of tackle is
improved, the art of angling refined, and the fish in once-famous
waters are educated or exterminated.

Alas, how transient is the fashion of this world, even in angling!
The old manuals with their precise instruction for trimming and
painting trout-rods eighteen feet long, and their painful
description of "oyntments" made of nettle-juice, fish-hawk oil,
camphor, cat's fat, or assafoedita, (supposed to allure the fish,)
are altogether behind the age.  Many of the flies described by
Charles Cotton and Thomas Barker seem to have gone out of style
among the trout.  Perhaps familiarity has bred contempt.  Generation
after generation of fish have seen these same old feathered
confections floating on the water, and learned by sharp experience
that they do not taste good.  The blase trout demand something new,
something modern.  It is for this reason, I suppose, that an
altogether original fly, unheard of, startling, will often do great
execution in an over-fished pool.

Certain it is that the art of angling, in settled regions, is
growing more dainty and difficult.  You must cast a longer, lighter
line; you must use finer leaders; you must have your flies dressed
on smaller hooks.