ENGINEER AND MACHINIST’S DRAWING-BOOK.
the intersections are very acute, the manner first described
above may be adopted.
As an additional illustration and example for practice,
we have thought it desirable to give (in Fig. 246) an isome-
trical projection of the pillow-block, shown geometrically in
Plate 12. And in proceeding to draw this subject (in this
respect unlike ordinary perspective), it is quite immaterial
at which point we begin. We may commence by drawing
first the bottom plate, or, as was here done, the circular
part, a' c h\ c b', c a' c. Many examples might be in-
troduced to show the applicability of this mode of projec-
tion to other parts of machinery, but its principles are so
obvious, and its practice, when these are mastered, so easy,
that to multiply examples would be mere surplusage. We
shall therefore close this subject with the remark and
caution, that although isometrical projection is a valuable
addition to the ordinary plan, section, and elevation of
the mechanical draughtsman, and may be most advantage-
ously used as explanatory of these, it does not give so
truthful a representation of an object as a proper perspec-
tive drawing. It should only be used, therefore, when
the object in view is the elucidation or explanation of a
subject, and never when pictorial representation alone is
intended. Within these limits it is of extended utility,
beyond them it is caricature.
GLASGOW: W. G. BLACK1E AND CO., PRINTERS, YILLAFIELD.