ENLARGING AND REDUCING PLANS 
object on the plan beneath. The position of the object is then lo- 
cated on the tracing paper or cloth along the same line and at rela- 
tively the same distance from the central point at the new scale. 
Instead of changing the scale each time it is often easier to multiply 
the original reading by the ratio of enlargement or reduction and 
plot the point without moving the scale. This method is similar to 
the work done at any one station of a stadia-transit survey or a 
plane-table survey. 
Parallel Courses and Proportional Measurements 
In reducing or enlarging a simple rectilinear outline drawing 
as of a building, field or outline survey, a very easy method is to 
tack a transparent paper or cloth over the drawing, then starting 
from some angle draw a line directly over the first side and of the 
required length at the new scale, draw through its end a line parallel 
to the second side and measure off the required proportional length. 
Continue in this way making the corresponding sides of the original 
and the new drawing parallel and proportional. The last course will 
coincide with the last course of the original and its farther end will 
coincide with the starting point. Lines drawn from the starting 
point through any angle of the new plan will pass through the 
corresponding angle of the original. 
A starting point may be taken and all the work done entirely 
to one side or within the original so long as all corresponding sides 
are drawn parallel and proportional. This method of reducing is 
similar to the use of the plane-table or oriented drawing board in 
locating a broken line from successive stations. It is merely a little 
different application of the radial method. 
The Pantograph Method 
The pantograph is a mechanical device consisting of two pairs 
of parallel bars so arranged that a pencil mounted on one bar will 
move in any direction at a definite relation to the motion of a tracer 
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