Part 7 (1/2)

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112. _Scarfing._--Cutting timber at an angle along its length, as the line A. Scarfing joints are variously made. The overlapping joints may be straight or recessed and provided with a key block B. When fitted together they are securely held by plates and bolts.

113. _Scotia Molding._--A sunken molding in the base of a pillar, so called from the dark shadow which it casts.

114. _Sill._--In carpentry the base piece, or pieces, A, on which the posts of a structure are set.

115. _Skew-Back._--The course of masonry, such as a stone, A, with an inclined face, which forms the abutment for the voussoirs, B, or wedge-shaped stones comprising the arch.

116. _Spandrel._--The irregular, triangular s.p.a.ce, A, between the curve of an arch and the enclosing right angle.

117. _Strut._--In general, any piece of a frame, such as a timber A, or a brace B, which resists pressure or thrust in the direction of its length.

[Ill.u.s.tration: _Fig. 118.-Fig. 123._]

118. _Stud, Studding._--The vertical timber or scantling, A, which is one of the small uprights of a building to which the boarding or plastering lath are nailed.

119. _Stile._--The main uprights of a door, as A, A; B, B, B, rails; C, C, mullions; D, D, panels.

_Tie Beam._--See _Queen Post_.

120. _Trammel._--A very useful tool for drawing ellipses. It comprises a cross, A, with grooves and a bar, B, with pins, C, attached to sliding blocks in the grooves, and a pen or stylus, D, at the projecting end of the bar to scribe the ellipse.

121. _Turret._--A little tower, frequently only an ornamental structure at one of the angles of a larger structure.

122. _Transom._--A horizontal cross-bar, A, above a door or window or between a door and a window above it. Transom is the horizontal member, and if there is a vertical, like the dotted line B, it is called a _Mullion_. See _Stile_.

123. _Valley Roof._--A place of meeting of two slopes of a roof which have their sides running in different directions and formed on the plan of a re-entrant angle.

CHAPTER VIII

DRAWING AND ITS UTILITY

A knowledge of drawing, at least so far as the fundamentals are concerned, is of great service to the beginner. All work, after being conceived in the brain, should be transferred to paper. A habit of this kind becomes a pleasure, and, if carried out persistently, will prove a source of profit. The boy with a bow pen can easily draw circles, and with a drawing or ruling pen he can make straight lines.

REPRESENTING OBJECTS.--But let him try to represent some object, and the pens become useless. There is a vast difference in the use of drawing tools and free-hand drawing. While the boy who is able to execute free-hand sketches may become the better artist, still that art would not be of much service to him as a carpenter. First, because the use of tools gives precision, and this is necessary to the builder; and, second, because the artist deals wholly with perspectives, whereas the builder must execute from plane surfaces or elevations.

FORMING LINES AND SHADOWS.--It is not my intention to furnish a complete treatise on this subject, but to do two things, one of which will be to show, among other features, how simple lines form objects; how shading becomes an effective aid; how proportions are formed; and, second, how to make irregular forms, and how they may readily be executed so that the boy may be able to grasp the ideas for all shapes and structural devices.

[Ill.u.s.tration: _Fig. 125._]

[Ill.u.s.tration: _Fig. 126._]

[Ill.u.s.tration: _Fig. 127._]

a.n.a.lYSIS OF LINE SHADING.--In the demonstration of this work I shall give an a.n.a.lysis of the simple lines formed, showing the terms used to designate the lines, curves, and formations, so that when any work is laid out the beginner will be able, with this glossary before him, to describe architecturally, as well as mathematically, the angles and curves with which he is working.

HOW TO CHARACTERIZE SURFACE.--Suppose we commence simply with straight lines. How shall we determine the character of the surface of the material between the two straight lines shown in Fig. 125? Is it flat, rounded, or concaved? Let us see how we may treat the surface by simple lines so as to indicate the configuration.

[Ill.u.s.tration: _Fig. 128._]