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. Watts advises the perusal of the prefaces and the index of a book, as they both give light on its contents. 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.