ver-like characteristics, that it was ranked near the beaver
in the systematic lists.

Now, however, the Voles, as these creatures ought rightly to be called,
are thought to be of sufficient importance to be placed by themselves,
and separated from the true beavers.

The voles constitute quite a large group of rodents, including several
animals which are popularly ranked among the mice.

One very remarkable characteristic of the voles is the structure of
their molar teeth.

Being rodents, they can have but two incisor teeth in each jaw, these
teeth being rootless, and so set in their sockets that they are
incessantly worn away in front, and as incessantly grow from the base,
take the curved form of their sockets, and act much like shears which
have the inestimable property of self-sharpening when blunted, and
self-renewal when chipped or actually broken off by coming against any
hard substance. Were the teeth to be without this power, the animal
would run a great risk of dying from hunger, the injured tooth not being
able either to do its own work, or to aid its companion of the opposite
jaw. Either tooth alone would be as useless as a single blade of a pair
of scissors.

There is another notable characteristic of these incisor teeth. If you
will examine the incisors of any rodent, whether it be a rat, a mouse, a
rabbit, or a beaver, you will see that the tips are "bevelled" off just
like the edge of a chisel. This shape is absolutely necessary to keep
the tooth in working order. How is this object to be attained?

In the solution of this problem we may see one of the many links which
connect art and nature.

Should our readers know anything of carpentering, let them examine the
structure of their chisels. They are not made wholly of hard steel, as
in that case they would be liable to snap, just as does the blade of a
foil when undue pressure is brought to bear upon it. Moreover, the
operation of sharpening would be extremely difficult.

So the blade of the chisel is merely faced with a thin plate of hardened
steel, the remainder being of softer material.

Now, it is not at all likely that the unknown inventor of the modern
chisel was aware of the analogy between art and nature, and would
probably have been very much surprised if anyone had stated that he had
borrowed his idea from the incisor teeth of the water-rat.

Yet he might have done so, for these teeth are almost wholly formed of
ordinary tooth matte