Elements of mechanical drawing by Sullivan Christine

Author:Sullivan, Christine [Gordon]. [from old catalog]
Language: eng
Format: epub, pdf
Tags: Mechanical drawing
Publisher: New York, Cincinnati [etc.] American book company
Published: 1893-03-25T05:00:00+00:00

SUGGESTIONS.

1. A cube is the type form for rectilinear objects.

2. A cylinder is the type form for curvilinear objects.

3. Appearances of objects depend on two conditions,— distance and position. Distance produces perspective ; position, fore-shortening.

4. Rectilinear objects in parallel perspective have one face represented by an actual drawing, and one vanishing point.

5. In ajigular perspective no face is represented by an actual view, and there are two vanishing points.

6. The circle, w^hen in full view, is represented by a circle ; when viewed obliquely, by an ellipse ; and when viewed edgewise, by a line.

7. The point of station where the observer stands is the base of an upright plane, which the observer is supposed to occupy. All objects below his eye are said to be below the level of the eye ; all above, above the level of the eye.

8. Vertical lines are always represented by vertical lines.

9. Horizontal lines or edges are represented by horizontal and oblique lines, — by horizontal lines when the edges are parallel to the plane of the observer ; by oblique lines when the edges make an angle with this plane.

10. Retreating lines above the eye seem to run down to a point on a level with the eye, and opposite to it ; those below the eye seem to run up to the same point.

11. The apparent width of foreshortened surface may be ascertained by pencil measuring in space, and the drawing tested by rules of perspective.

12. Lines that are at an angle to the observer, and parallel in the object, vanish to one point in the drawing.

Exercise for Practice. —Make perspective sketches of cube, prisms, cylinder, cone, and pyramids.

Note i. — "Make three drawings of each object : first view, directly in front of the observer ; second view, to the left ; and third view, to the right.

Note 2. — See " Elements of Perspective for Schoolroom and Workshop."

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