the
full force of which, as I said before, I am indebted to John Richards;
and I would here add that the mechanic who has never learned anything
from John Richards is either a very good or very poor one, or has
never read what John Richards has written or heard what he has had to
say.

Three models, as shown in Fig. 1, were exhibited; all were of the same
general dimensions and containing the same amount of material. The one
made on the box principle, c, proved to be fifty per cent. stiffer
in a vertical direction than either a or b, from twenty to fifty
times stiffer sidewise, and thirteen times more rigid against torsion
than either of the others.

However strong a frame may be, its own weight and the weight of the
work upon it tends to spring it unless evenly distributed, and to
twist it unless evenly proportioned. For all small machines the single
post obviates all trouble, but for machine tools of from twice to a
half dozen times their own length the single post is not available.
Four legs are used for machines up to ten feet or so, and above that
legs various and then solid masonry. If the four legs were always set
upon solid masonry, and leveled perfectly when set, no question could
be raised against the usual arrangement, unless it be this: Ought they
not to be set nearly one-fourth the way from the end of the bed? or to
put it in another form: Will not the bed of an iron planing machine
twelve feet in length be equally as well supported by four legs if
each pair is set three feet from the ends--that is, six feet apart--as
by six legs, two pairs at the ends and one in the center, and the
pairs six feet apart? there being six feet of unsupported bed in
either case, with this advantage in favor of the four over the six,
settling of the foundation would not bend the bed.

It is not likely that one-half of the four-legged machine tools used
in this country are resting upon stable foundations, nor that they
ever will be; and while this is a fact, it must also remain a fact
that they should be built so as to do their best on an unstable one.
Any one of the thousand iron planing machines of the country, if put
in good condition and set upon the ordinary wood floors, may be made
to plane work winding in either direction by shifting a moving load of
a few hundred pounds on the floor from one corner of the machine to
the other, and the ways of the ordinary turning lathe may be more
easily distorted still. Machine tool