This section is from the "The elements of drawing & the elements of perspective" book, by J. M. Dent & Sons. Also see Amazon: The Elements Of Drawing & The Elements Of Perspective.
If you cannot get either a Rembrandt or a Durer, you may still learn much by carefully studying any of George Cruikshank's etchings, or Leech's woodcuts in Punch, on the free side; with Alfred Rethel's and Richter's l on the severe side. But in so doing you will need to notice the following points:
When either the material (as the copper or wood) or the time of an artist, does not permit him to make a perfect drawing, - that is to say, one in which no lines shall be prominently visible, - and he is reduced to show the black lines, either drawn by the pen, or on the wood, it is better to make these lines help, as far as may be, the expression of texture and form. You will thus find many textures, as of cloth or grass or flesh, and many subtle effects of light, expressed by Leech with zigzag or crossed or curiously broken lines; and you will see that Alfred Rethel and Richter constantly express the direction and rounding of surfaces by the direction of the lines which shade them. All these various means of expression will be useful to you, as far as you can learn them, provided you remember that they are merely a kind of shorthand; telling certain facts, not in quite the right way, but in the only possible way under the conditions: and provided in any after use of such means, you never try to show your own dexterity; but only to get as much record of the object as you can in a given time; and that you continually make efforts to go beyond such shorthand, and draw portions of the objects rightly. See, for account of these plates, the Appendix on Works to be studied.
And touching this question of direction of lines as indicating that of surface, observe these few points:
If lines are to be distinctly shown, it is better that, so far as they can indicate anything by their direction, they should explain rather than oppose the general character of the object. Thus, in the piece of woodcut from Titian, Fig. 10., the lines are serviceable by expressing, not only the shade of the trunk, but partly also its roundness, and the flow of its grain.And Albert Durer, whose work was chiefly engraving, sets himself always thus to make his lines as valuable as possible; telling much by them, both of shade and direction of surface: and if you were always to be limited to engraving on copper (and did not want to express effects of mist or darkness, as well as delicate forms), Albert Durer's way of work would be the best example for you. But, inasmuch as the perfect way of drawing is by shade without lines, and the great painters always conceive their subject as complete, even when they are sketching it most rapidly, you will find that, when they are not limited in means, they do not much trust to direction of line, but will often scratch in the shade of a rounded surface with nearly straight lines, that is to say, with the easiest and quickest lines possible to themselves.
When the hand is free, the easiest line for it to draw is one inclining from the left upwards to the right, or vice versa, from the right downwards to the left; and when done very quickly, the line is hooked a little at the end by the effort at return to the next. Hence, you will always find the pencil, chalk, or pen sketch of a very great master full of these kind of lines; and even if he draws carefully, you will find him using simple straight lines from left to right, when an inferior master would have used curved ones. Fig. 11. is a fair facsimile of part of a sketch of Raphael's, which exhibits these characters very distinctly. Even the careful drawings of Leonardo da Vinci are shaded most commonly with straight lines; and you may always assume it as a point increasing the probability of a drawing being by a great master if you find rounded surfaces, such as those of cheeks or lips, shaded with straight lines.
But you will also now understand how easy it must be for dishonest dealers to forge or imitate scrawled sketches like Figure II, and pass them for the work of great masters; and how the power of determining the genuineness of a drawing depends entirely on your knowing the facts of the object drawn, and perceiving whether the hasty handling is all conducive to the expression of those truths. In a great man's work, at its fastest, no line is thrown away, and it is not by the rapidity, but the economy of the execution that you know him to be great. Now to judge of this economy, you must know exactly what he meant to do, otherwise you cannot of course discern how far he has done it; that is, you must know the beauty and nature of the thing he was drawing. All judgment of art thus finally founds itself on knowledge of Nature.
But farther observe, that this scrawled, or economic, or impetuous execution is never affectedly impetuous. If a great man is not in a hurry, he never pretends to be; if he has no eagerness in his heart, he puts none into his hand; if he thinks his effect would be better got with two lines, he never, to show his dexterity, tries to do it with one. Be assured, therefore (and this is a matter of great importance), that you will never produce a great drawing by imitating the execution of a great master. Acquire his knowledge and share his feelings, and the easy execution will fall from your hand as it did from his; but if you merely scrawl because he scrawled, or blot because he blotted, you will not only never advance in power, but even' able draughtsman, and every judge whose opinion is worth having, will know you for a cheat, and despise you accordingly.