The ravenous appetite of Johnson for reading is expressed in a strong metaphor by Mrs. Knowles, who said, “he knows how to read better than any one; he gets at the substance of a book directly:  he tears out the heart of it.”  Gibbon has a new idea in the “Art of Reading;” he says “we ought not to attend to the order of our books so much as of our thoughts.  The perusal of a particular work gives birth perhaps to ideas unconnected with the subject it treats; I pursue these ideas, and quit my proposed plan of reading.”  Thus in the midst of Homer he read Longinus; a chapter of Longinus led to an epistle of Pliny; and having finished Longinus, he followed the train of his ideas of the sublime and beautiful in the “Enquiry” of Burke, and concluded by comparing the ancient with the modern Longinus.

There are some mechanical aids in reading which may prove of great utility, and form a kind of rejuvenescence of our early studies.  Montaigne placed at the end of a book which he intended not to reperuse, the time he had read it, with a concise decision on its merits; “that,” says he, “it may thus represent to me the air and general idea I had conceived of the author, in reading the work.”  We have several of these annotations.  Of Young the poet it is noticed, that whenever he came to a striking passage he folded the leaf; and that at his death, books have been found in his library which had long resisted the power of closing:  a mode more easy than useful; for after a length of time they must be again read to know why they were folded.  This difficulty is obviated by those who note in a blank leaf the pages to be referred to, with a word of criticism.  Nor let us consider these minute directions as unworthy the most enlarged minds:  by these petty exertions, at the most distant periods, may learning obtain its authorities, and fancy combine its ideas.  Seneca, in sending some volumes to his friend Lucilius, accompanies them with notes of particular passages, “that,” he observes, “you who only aim at the useful may be spared the trouble of examining them entire.”  I have seen books noted by Voltaire with a word of censure or approbation on the page itself, which was his usual practice; and these volumes are precious to every man of taste.  Formey complained that the books he lent Voltaire were returned always disfigured by his remarks; but he was a writer of the old school.[A]

[Footnote A:  The account of Oldys and his manuscripts, in the third volume of the “Curiosities of Literature,” will furnish abundant proof of the value of such disfigurations when the work of certain hands.—­ED.]

A professional student should divide his readings into a uniform reading which is useful, and into a diversified reading which is pleasant.  Guy Patin, an eminent physician and man of letters, had a just notion of this manner.  He says, “I daily read Hippocrates, Galen, Fernel, and other illustrious masters of my profession; this I call my profitable readings.  I frequently read Ovid, Juvenal, Horace, Seneca, Tacitus, and others, and these are my recreations.”  We must observe these distinctions; for it frequently happens that a lawyer or a physician, with great industry and love of study, by giving too much into his diversified readings, may utterly neglect what should be his uniform studies.