Scale of Degrees in Line
There are the qualities of line in different degrees of firmness, roughness, raggedness, or smooth and flowing. There are the degrees of direction of line, curvilinear or angular. On the angular side all variations from the perpendicular and horizontal, or rectangle, within which we may find all these degrees, and on the curvilinear side, all the variations from spiral to circle: so that we might say that the rectangle was the cradle of all angular variations of line, while the semicircle was the cradle of all curvilinear variations. (See the diagrams on p. [26].)
Every artist, sooner or later, by means of his selective adaptive sense, finds a method in the use of line to suit his own personality—to suit his own individual aim in artistic expression—and in course of time it becomes a characteristic manner, by which his work is instantly known, like a friend's handwriting.
Now what determines this choice, this personal selection, over and above necessities of method and material, it would be difficult to say, unless we had more minute knowledge of the natural history of a human being than we are likely to possess. We can only say that from practice are evolved certain methods or principles, consciously or unconsciously; and it is only these general methods or principles that can be explained and tested for the benefit of those essaying to follow the arduous and difficult path of art.
Relation of Line to Form
At the outset we see that we need a means of definition in drawing, just as a child needs a word to express a thing it wants. Line, at the point of the pencil, pen, or brush, places this possibility of definition within our reach; but before we can grasp it we need some knowledge, however rudimentary, of its inseparable companion, Form.