In fact, all
the contrivance, and all the improvements, ought first to be
represented in the drawings.
320. On the other hand, there are effects dependent upon
physical or chemical properties for the determination of which no
drawings will be of any use. These are the legitimate objects of
direct trial. For example; if the ultimate result of an engine is
to be that it shall impress letters on a copperplate by means of
steel punches forced into it, all the mechanism by which the
punches and the copper are to be moved at stated intervals, and
brought into contact, is within the province of drawing, and the
machinery may be arranged entirely upon paper. But a doubt may
reasonably spring up, whether the bur that will be raised round
the letter, which has been already punched upon the copper, may
not interfere with the proper action of the punch for the letter
which is to be punched next adjacent to it. It may also be feared
that the effect of punching the second letter, if it be
sufficiently near to the first, may distort the form of that
first figure. If neither of these evils should arise, still the
bur produced by the punching might be expected to interfere with
the goodness of the impression produced by the copperplate; and
the plate itself, after having all but its edge covered with
figures, might change its form, from the unequal condensation
which it must suffer in this process, so as to render it very
difficult to take impressions from it at all.
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