of the rod; a lever actuating a plunger in a vertical line, to find how much a given amount of motion of the long arm will actuate the plunger

226 Two levers upon their axles or shafts, the arms connected by a link and one arm connected to a rod 227 A lever arm and cam in one piece on a shaft, a shoe sliding on the line, and held against the cam face by the rod, to find the position of the face of the shoe against the cam 228 To find the amount of motion imparted in a straight line to a rod, attached to an eccentric strap 229 Examples in drawing the cut off cams employed instead of eccentrics on river steamboats in the Western and Southern States. Different views of a pair of cams 232 The object of using a cam instead of an eccentric 234 Method of drawing or marking out a full stroke cam 237 Illustration of the lines embracing cut off cams of varying limits of cut-off 240 Part played by the stroke of the engine in determining the conformation of cut-off cams; manner of finding essential points of drawings of cutoff cams 241 A cam designed to cut off the steam at five-eighths of the piston stroke 244 Three-fourths and seven-eighths cams 246 Necessary imperfections in the operations of cut-off cams 247 Drawing representing the motion which a crank imparts to a connecting rod 249 Plotting out the motion of a shaper link quick return 250 Plotting out the Whitworth quick return motion employed in machines 253 Finding the curves for moulding cutters 257

CHAPTER XIII.

EXAMPLES IN LINE-SHADING AND DRAWING FOR LINE-SHADED ENGRAVINGS.

Arrangement of idle pulleys to guide bolts from one pulley to another; representation of a cutting tool for a planing machine 264 Drawings for photo-engraving 267

Drawing for an engraver in wood; drawings for engravings by the wax process 268 Engraving made by the wax process from a print from a wood engraving; engravings of a boiler drilling machine 269

CHAPTER XIV.

SHADING AND COLORING DRAWINGS.

Coloring the journals of shafts; simple shading; drawing cast-iron, wrought iron, steel and copper 277 Points to be observed in coloring and shading; colored drawings to be glued around their edges to the drawing board; to maintain an even shade of color; mixing colors 278 To graduate the depth of tint for a cylindrical surface 279 The size and use of brushes; light in shading; example for shading a Medart pulley 280 Brush shading 281 To show by the shading that the surfaces are highly polished; representation of an oil cup; representation of an iron planing machine 282