g remains but tumultuous sensations.

To account for these different effects, we must have recourse to a logical
distinction, which appears to reveal one of the great mysteries in the
art of reading. Logicians distinguish between perceptions and ideas.
Perception is that faculty of the mind which notices the simple impression
of objects: but when these objects exist in the mind, and are there
treasured and arranged as materials for reflection, then they are called
ideas. A perception is like a transient sunbeam, which just shows the
object, but leaves neither light nor warmth; while an idea is like the
fervid beam of noon, which throws a settled and powerful light.

Many ingenious readers complain that their memory is defective, and their
studies unfruitful. This defect arises from their indulging the facile
pleasures of perceptions, in preference to the laborious habit of forming
them into ideas. Perceptions require only the sensibility of taste, and
their pleasures are continuous, easy, and exquisite. Ideas are an art of
combination, and an exertion of the reasoning powers. Ideas are therefore
labours; and for those who will not labour, it is unjust to complain, if
they come from the harvest with scarcely a sheaf in their hands.

There are secrets in the art of reading which tend to facilitate its
purposes, by assisting the memory, and augmenting intellectual opulence.
Some our own ingenuity must form, and perhaps every student has peculiar
habits of study, as, in sort-hand, almost every writer has a system of his
own.

It is an observation of the elder Pliny (who, having been a voluminous
compiler, must have had great experience in the art of reading), that
there was no book so bad but which contained something good. To read every
book would, however, be fatal to the interest of most readers; but it is
not always necessary, in the pursuits of learning, to read every book
entire. Of many books it is sufficient to seize the plan, and to examine
some of their portions. Of the little supplement at the close of a volume,
few readers conceive the utility; but some of the most eminent writers in
Europe have been great adepts in the art of index reading. I, for my part,
venerate the inventor of indexes; and I know not to whom to yield the
preference, either to Hippocrates, who was the first great anatomiser of
the human body, or to that unknown labourer in literature, who first laid
open the nerves and arteries of a book.