late; side elevation of the cylinder, with end
view of the same 299

Steam chest side and horizontal cross section of the cylinder; steam chest
and the valves; cam wrist plate and cut-off mechanism; shaft for the
cam plate; cross head; side view and section through the centre of
the eccentric and strap 301

Construction of the connecting rod 303

INDEX 305

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|Transcriber's note: In this text $T$ indicates a larger capital letter.|
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MECHANICAL DRAWING

SELF-TAUGHT.

CHAPTER I.

_THE DRAWING BOARD._

A Drawing Board should be of soft pine and free from knots, so that it
will easily receive the pins or tacks used to fasten down the paper. Its
surface should be flat and level, or a little rounding, so that the
paper shall lie close to its surface, which is one of the first
requisites in making a good drawing. Its edges should be straight and at
a right angle one to the other, and the ends of the battens B B in
Figure 1 should fall a little short of the edge A of the board, so that
if the latter shrinks they will not protrude. The size of the board of
course depends upon the size of the paper, hence it is best to obtain a
board as small as will answer for the size of paper it is intended to
use. The student will find it most convenient as well as cheapest to
learn on small drawings rather than large ones, since they take less
time to make, and cost less for paper; and although they require more
skill to make, yet are preferable for the beginner, because he does not
require to reach so far over the board, and furthermore, they teach him
more quickly and effectively. He who can make a fair drawing having
short lines and small curves can make a better one if it has large
curves, etc., because it is easier to draw a large than a very small
circle or curve. It is unnecessary to enter into a description of the
various kinds of drawing boards in use, because if the student purchases
one he will be duly informed of the kinds and their special features,
while if he intends to make one the sketch in Figure 1 will give him all
the information he requires, save that, as b