•— 244 —— 
IX., Figs. 3 and 6.) 
Burr. 一 A rough edge cr ;.idge left by a tool in cutting metal. The term is sometimes used 
for a nut. 
BuUon Sett. — A tool for fornüng the heads of rivets. (Plato XII., Fig. 5.) 
Camber. — The upward curvature of a truss. It is measured by the height of tbo middle 
point of the centre line of the lower chord above tlie line joining the contres of end pins. 
Camber Blocks. — Blocks of wood used in erection, so placed as to be easily removed. 
(Plate XI.) 
Cape Chisel. — A tool for cutting iron. It consists of a rounded edge on the end of a short 
rod. The edge is very obtuse, so as not to break easily. 
Centre of Gravity. — That point of a body about which the weights of all the different 
portions balance. 
Channel, or ciuinnel Bar. — Iton rolled into the shape shown in section on Plate II” 
Fig. 1. 
Ciieclc Nut, «r Lock Nut. 一 A contrivance to prevent a nnfc from turning* when subjccte a 
to shock. 
ciiord. 一 - The upper or lower part of a truss, usually horizontal, resisting- compression o r 
tension. (Plate I.) 
Cl&ora Bar. — - A member of the chord which is subjected to tension. (Plate I.) 
Chord Ilea«!. — The enlarged end of a chord bar, through which the pin passes. 
Chord Pncicing. — The arrangement of the bottom chord of a truss. 
Clear Headway. — The vertical distance from tlie upper surface of the rails to tbe lowest 
part of the overlieiid bracing. It is a measure of tlio height of the highest car that could pass 
through the bridge. 
Clear Roadway. 一 The horizontal distance, 7iieasnred perpendicularly to tlie planes 
tho trusses, between the inner edges of the batter braces. It is a measure of the width of the 
widest car that could pass through the bridgo. 
Cleat. — A narrow strip of wood nailed to something for the purpose of keeping a piece J 
work in its proper place. 
Co-eiilcient of Friction. 一 A numerical quantify, which, multiplied into the normal pres- 
sure， gives the frictional resistance. It is equal to the natural tangent of the angle of repose* • 
C’oltl Cliisel. — A tool for cutting iron. (Plate XII., Fig. 12.) 
Column. 一 A pillar or strut; a 1011 ^ member which resists compression. 
Component. — Ono of the parts into which a stress may be resolved or divided. 
€ompres«ioii. — A stress which tends to she r ton tlie member which is subjected to it. 
Concentrated Load. — A load which is, or may ho considered, collected atone or more poi 0 ^* 
Connecting-Plat«». 一 A plate used for connecting two pieces. 
Continuous ^paiis. — Consecutive spans connected over the points of support. 
Counter. — An adjustable diagonal which is not subjected to stress by a uniformly disti ’ レ 
buted load covering the bridge. (Plate I.) 
Countersunk Rivets. — Rivets, the heads of which are let into one or both of the pl ateS 
which they connect, so as to leave a flxish surface or surfaces. 
Couple. — Two equal and parallel forces not acting in the same line. 
Cover Plate. — A plate used to cover a joint, or to connect two pieces of tlie toi) chord 切 . 
(Plate II., Fig. 11.) 
Crab. — A slow-motion machine, worked by a crank for the purpose of winding a rope 
a drum, thereby raising a heavy weight. (Plate XII., Fig. 1.) 
Crow Bar. — An iron lever. (Plate XII., Fig. 17.) 
Curvature Stre*s( ， a • — Stresses produced by the centrifugal force of passing trains, ^ e1X 
the bridge is on a curve. 
Dap. 一 To notch timber onto its bearing. 
I>ead Load. — The weight of all the^parts of the bridge itself, and any thing that ^ 
