1. Architecture is the art of designing and constructing buildings.
2. The designing of buildings consists in a graphic (or plas tic) represertation of their intended shapes and sizes.
3. An architect uses mechanical drawing to express his ideas and to'record exactly the size and shape of the object represented.
4. In mechanical drawing, the instruments used to draw the straight lines the curves which express the forms of objects, are, among others, the straight edge, triangle and compass.
5. In general, full straight lines indicate visible edges, and broken or dotted lines indicate relations of different parts, such as the axis or center-line of a street or building or the distance covered by a figured meas urement.
6. Horizontal lines are drawn along a T-square , whose head rests against theleft side of a drawing board.
Vertical and sloping lines are drawn against a triangle rest ing against the T-square.
(Fig. 1).
7. Two horizontal lines intersecting two ver t ic al lines, all of equal length, form a sqUare. If its opposite corners are connected by straight lines, called diagonals, the intersection of these diagonals gives the center of the square. A horizontal and a vertical line may be drawn through this center, and then, by setting the point of the compass at the center and opening the compass along either of these lines to the sides of the square, a circle may be .drawn which will be exactly inscribed within the square. The square itself will be divided into four small squares, each of which contains a quadrant or quarter circle. (C, plan, Fig. 2.) 8. The circle is divided into 360 parts, which are used for measuring angles or the difference in direction between any two lines that meet in the center of the circle. For convenience, an instrument called a protractor is sometimes used, which consists of a half-circle divided into 180 parts called degrees (a). A vertical line from the center of the circle will cut the curve or circumfer ence at a point 90° above the horizontal, and the diagonals of the square in which the circle is inscribed will divide each angle of 90° into two angles of 45° each.
9. As it is impracticable to draw many objects at their full size, an arbitrary scale is used to enable the drawing to be made at a, or some other fraction of its true size. Drawings at the scale of inch to the foot reproduce each dimension of an object at of its true size. The system of drawing things " to scale" enables us to make accurate drawings at any convenient size. •
10. To make pictures of objects in such a way as to express accurately the size and shape of every part, three drawings are usually necessary—a plan, a section, and an elevation—the plan to show widths and lengths, the section to show widths and heights, the elevation to show lengths and heights.
11. A drawing looks better when its perpendicular center is half-way across the paper and its bulk placed slightly above the horizontal center of the sheet. Begin then by finding a point in the paper half-way between the sides, and through this center draw a vertical line— the vertical axis of the drawing. Lay out the plan, the elevation, or the sum of the two together with the space between them, so that half the finished work shall be on each side of the vertical axis.
12. In mechanical drawing, it is best to begin by indicating the axes or center lines of objects in plan, section and elevation. On either side of these axes lay out one-half of the width or depth of the objects represented.
13. A pier or pillar is a mass of stone, wood or metal stand ing on end and used as a support. (Fig. 2, C.) 14. A lintel is a piece of stone, timber, or metal laid flat upon two pillars so as to form an opening or bay. (Fig. 2, E.) 15. A string course is a horizontal of stone, brick, or other building material projecting beyond the face of a wall. (Fig. 2, F.) 16. The first exercise, Fig. 2, shows two pillars C and D, carrying a lintel E, above which is a string course F. The plan shows the width and the depth of the pillars C and D. It shows that pillar D is square and that pillar C is eight sided (octagonal.) It also shows that these two pillars are set along a straight line or axis (A-B) having the same direction as two of their sides. The section shows the vertical position, the depth and the height of the pillars, the width and the height of the 'lintel E, which rests on the pillars so as to line with their face; and last of all the height and the width of the string course F, with its tion beyond the lintel E. The elevation shows the general rangement of pillars and lintel as seen from an arbitrary point directly in front. It shows that the two pillars are upright or plumb, indicates the shape of the space between, and gives the length of the lintel and of the string course.