=Outline.=--In the early engravings the constructive element consisted almost entirely of pure outline, which was rarely monotonous, but frequently suggestive of form and character. Is it not almost marvellous, this suggestive power of outline, for is it not in reality but an imaginary boundary? An actual outline is a thing unknown in nature, and the very fact that it has its existence only in the imagination of the artist makes our reconciliation to it and our admiration of it the more wonderful. The astonishing elasticity of the human imagination makes it quite easy to fill in the details of a picture if only the outline be sufficiently suggestive. The primary function of the outline is, of course, to represent; but its secondary or suggestive purpose is scarcely of less importance, and can only be fully realised when the imagination is so stimulated as to perceive more than is actually exhibited. The completeness and truthfulness of the outline must be an engraver's first point. An art critic once stated that "He had finished the picture who had finished the outline." To some extent such a statement may be perfectly true; but just as in elocution, or even in ordinary conversation, emphasis is requisite, so in pictorial art the emphasis of concise expression, modulation, and delicate or vigorous accentuation are equally necessary and effective. =Extraneous Matter.=--In other words, an artist's ideas may be decisively portrayed in outline, yet for lack of suitable extraneous matter appear both crude and impoverished. The amount of characteristic form expressed by constructive elements in the drawing, other than the outlines, is strikingly illustrated in old German portrait engravings. They are simply overflowing with details of the most minute description. Nor can such details be regarded as altogether superfluous, for they each help to _build up_ the character of the picture. In portrait engraving a mere likeness may easily be portrayed by a simple outline. Not so, however, with character. Considerable amplification will be necessary to show that; and this, perhaps, is the most difficult task of the engraver--to introduce a satisfactory amount of essential detail without detracting in any way from a pleasing general effect in the picture.