1. This
is covered with a brass plate, c, pierced with a hole one-half of an inch
in diameter. This hole extends through the wood, and is fitted with a
piston. Two long narrow inclined planes of nearly equal inclination, b,
b, grooved to slide on each other, are placed under the bridge; the lower
is to be fastened to the board; the end of the piston rests on the upper
one. The object from which we desire to cut a section is placed in the
hole, in the piston. If the upper plane be pushed in, the piston will be
forced upward, and with it the object. As the inclination of the plane is
very gradual, the vertical motion will be very slight as compared with
the horizontal.
When the object is raised a little above the brass plate, a keen edged
razor, thoroughly wet, is pushed over the hole, cutting the object. This
gives the section a smooth surface, and even with the plate; now push the
plane forward one-eighth to one-quarter of an inch, and cut again; this
will give a thin section of the object. The thickness of the section
depends, of course, on the distance the wedge is pushed.
With a little practice, much better sections can be cut by the hand than
by any machine; this does not apply of course to large sections.
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