by signs the action of machinery. 
257 
line attached to the part. — 
If the distance between two 
parts, which are represented by different lines, is to be al- 
tered, their lines may be connected by an horizontal line. 
A D 
Thus the adjustment of A in the above figure depends on 
its distance from D. 
This adjustment often determines the length of a stroke, and 
sometimes the eccentricity of an eccentric, which depends on 
the linear distance between its centre and its centre of motion. 
The next most frequently occurring adjustment is that 
which is sometimes necessary in fixing two wheels, or a wheel 
and an arm on the same axis. This relation of angular posi- 
tion, may be indicated by a circle and two radii placed at 
the requisite angle, or that angle may be stated in figures 
and inclosed within the circle ; this circle ought however to 
be connected by a line with the other part, with which the 
angle is to be formed, thus, 
which means that an adjustment is to be made by fixing A on 
its axis, making a right angle with D, and that F must also 
make with C an angle of sixty degrees. In speaking of these 
angles, it should always be observed that they refer to the 
angles made by the parts on one of the planes of projection. 
