in another, apparently in defiance of all rules of the
strength of material; if you have endeavored to ascertain why a
particular device is used rather than another more evident one; if you
have thought and studied why a boss is thrown in here and there in
designs to receive bolts or to lengthen a journal, and if you have in
your mind, by repeated observation, a fair idea of how work is
designed by other people, the so-called _mechanical intuition_ will be
learned and found to be the _combination of common sense and good
practice_.

You will observe that some details have been copied for years and
years, although thoughtful men would say they are not the best, simply
because they are adapted to a large amount of work already done. This
is particularly true of the rolling stock on railroads. The cost of a
change in starting in a new country might be warranted, but it
practically cannot be done when the parts must interchange with so
much work done in other parts of the country. You will find in other
cases that the direct strain to which a piece of mechanism is
subjected is only one of the strains which occur in practice. A piece
of metal may have been thickened where it customarily broke, and you
may possibly surmise that certain jars took place that caused such
breakages, or that particular point was where the abuse of the
attendant was customarily applied.

Wherever you go you will find matters of this kind affecting designs
staring you in the face, and you will soon see why a man who has
learned his trade in the shop, and from there worked into the drawing
room with much less technical information than you have, can get along
as well as he does. Reserve your strength, however. Your time will
come. Whenever there is a new departure to be taken, and matters to be
worked out from the solid which require close computation of strains
or the application of any principles, your education will put you far
ahead, and if you have, during the period of what may be called your
post-graduate course, which occurs during your early introduction into
practical life, been careful to keep your eyes and ears open so as to
learn all that a man in practical life has done, you will soon stand
far ahead.

Reference was made to the use of leisure hours. Leisure hours can be
spent in various ways. For instance, in studying the composition and
resolution of forces and the laws of elasticity in a billiard room,
the poetry of motion, etc.,