The blackboard has been well called the great weapon of the modern educator; this is especially true in reference to instruction in an art dealing with lines, curves and figures. Many a man can chalk out on a blackboard, or on a piece of sheet-iron, or on the floor, just what he wants. to show, and make his meaning very plain; hence, in every workshop, and many other places, a blackboard Fig. 6. is more than useful, and it has been said that no draughting office is complete without one. Fig. 6 represents a chalk-crayon. Fig. 8. Figs. 7 and 8 need no explanation, as they represent two forms of the well-known blackboard. Chalk lines have this advantage-they are easily altered or rubbed out when not needed any longer. The work executed upon a blackboard is mostly done by hand, without aid from instruments; a few tools, however, are useful-such as, 1, large wooden blackboard compasses holding a crayon, which are made and sold by the trade in size twelve inches to thirty inches in length; 2, a straight-edge; and 3, some crayons. With the compasses circles and part of the circle can be made, and with the straight-edge the larger lines can be drawn. These instruments are shown on page 29, and are, I, compasses, for holding chalk for making circles; 2, a tee-square; 3, a straight-edge; 4, a protractor for measuring angles; 5, a triangle 60° and 30°; 6, a brass holder for crayons. Blackboard Drawing.-The use of a blackboard comes principally and properly under the head of free-hand drawing, but its importance is such that a separate division of the volume is assigned to it. Thus, chalk-work may be considered the first lesson in "free-hand," as all the examples can also be most profitably practiced with pencil and paper. Very rapid drawing upon the board should not be encouraged, as it is likely not to be accurate enough; again, the board should be entirely free from grease. Cloths, sponges or chamois skin rubbers may be used to erase or change the chalk marks. Vertical lines should be drawn from above downward; short lines should be drawn with the fingers alone, those somewhat longer with the hand, using the wrist-joint; the still longer lines with the forearm, using the elbow-joint; those longer yet with the whole arm, using the shoulder-joint; lines should always be drawn with a uniform motion, slow enough for the eye to follow. Practice in chalk-work should alternate with sketching in a sketchbook and with geometrical drawing to be hereafter described. The student should practice a short time on the board, at least once a week; large sizes are the most profitable for the representations to be made; when drawing in different directions the hand should be turned, not the paper or board; the hand should never be allowed to obstruct the sight, hence the hand and fingers should be held in a position of freedom-with fingers not nearer than 1% or 2 inches from the board. PREPARATORY PRACTICE IN DRAWING. Every visible object is bounded by lines which enable the observer to determine its shape. If these NOTE. The first lesson of any kind the author received in drawing was to make a straight line; this was effected by holding the pencil nearly erect and guiding it along by the aid of the little finger held pressed against the edge of a board; this was a useful item of knowledge, as proved by passing years. A well-known artist, in telling his early experience, said: "The first thing I was taught was to draw a line, divide it, erect a perpendicular from its center, and afterwards to divide the angle made by the perpendicular." In answer to a question asking how long he was kept at the lines, he replied, "about two months-or a month or two," indicating that even the longer time would have been well spent in learning to draw a straight line. |