ng edge, either along or across the
grain. It is well illustrated in cutting soft materials, such as
bread, meat, rubber, cork, etc. It is an advantage in delicate
chiseling and gouging. That this sliding action is easier than the
straight pressure can easily be proved with a penknife on thin wood,
or by planing with the plane held at an angle to, rather than in line
with, the direction of the planing motion. The edge of the cutter then
slides into the material. The reason why the sliding cut is easier,
is partly because the angle of the bevel with the wood is reduced
by holding the tool obliquely, and partly because even the sharpest
cutting edge is notched with very fine teeth all along its edge so
that in the sliding cut it acts like a saw. In an auger-bit, both
methods of cutting take place at once. The scoring nib cuts with a
sliding cut, while the cutting lip is thrust directly into the wood.

The chisel and the knife, one with the edge on the end, and the
other with the edge on the side, are the original forms of all modern
cutting tools.

The _chisel_ was at first only a chipped stone, then it came to be a
ground stone, later it was made of bronze, and still later of
iron, and now it is made of steel. In its early form it is known
by paleontologists as a celt, and at first had no handle, but later
developed into the ax and adze for chopping and hewing, and the chisel
for cuts made by driving and paring. It is quite likely that the celt
itself was simply a development of the wedge.

In the modern chisel, all the grinding is done on one side. This
constitutes the essential feature of the chisel, namely, that the back
of the blade is kept perfectly flat and the face is ground to a bevel.
Blades vary in width from 1/16 inch to 2 inches. Next to the blade on
the end of which is the cutting edge, is the shank, Fig. 65. Next, as
in socketed chisels, there is the socket to receive the handle, or,
in tanged chisels, a shoulder and four-sided tang which is driven into
the handle, which is bound at its lower end by a ferrule. The handle
is usually made of apple wood.

[Illustration: Fig. 65. Firmer-Chisel.]

The most familiar form is the _firmer-chisel_, Fig. 65, which is said
to get its name from the fact that it is firmer or stiffer than the
paring-chisel. (See below.) The firmer-chisel is a general utility
tool, being suited for hand pressure or mallet pounding, for paring or
for light mortising.

Different vari