SCALING PLANS 
though originally made to standard scales, are now “‘out of scale” 
because they have been reduced in size in the process of engraving. 
Any photographic reproduction of a map or plan is likely to change 
the scale in this manner; and drawings, especially blueprints, often 
shrink appreciably so as to make the use of the standard scale im- 
practicable. 
Whenever such a drawing contains a proper graphic scale it 
will be easy to read any measurements. If necessary a longer scale 
can be constructed on a piece of drawing paper by copying and 
extending the graphic scale. If no graphic scale is given one can 
still be made providing the true length of any line in the drawing is 
known or can be ascertained. This known length can then be sub- 
divided and a graphic scale constructed. 
It is important that all these considerations be fully understood 
by the pupil for they will be found essential in handling the exercises 
assigned in this book. 
Practice 
The pupil at this point should have considerable practice in 
reading distances on plans and maps of all sorts. Besides the nu- 
merous examples found in this book he should examine maps in 
geographies, plans of architects, building and bridge plans in books 
of all sorts, and should make sure that he can determine quickly and 
accurately any measurements shown on any legible plan or map 
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