The next step was the substitution of light forms stiffened by the wires
being tensioned over them. This was the invention of Professor Roeder,
recently deceased. The next step was the common counter scale, and then
that form of letter scale in which one of the bands acts as a fulcrum
and the other as a pivot.

After Professor Roeder's death, Dr. Alfred Springer, of Cincinnati,
continued perfecting this invention, and with marked success--scales not
intended for anything but the weighing of the ordinary articles of a
grocery store working so accurately that up to 50 lb. two grains would
turn the balance.

As will be noted, this balance dispenses entirely with knife edges, and
this statement carries with it the gist of its entire merit. There is no
friction, and the elegance of the work and the nice adjustments of the
parts struck the writer at once.

[Illustration: KENT'S TORSION BALANCE. Fig 5.]

The prescription scale and the proportional scale (see Fig. 4) are
particularly interesting. The former is sensitive to 1/64 of a grain,
and the latter, invented by Mr. Kent, is a most ingenious method for
weighing, by which, in a small compass (10½ in. by 4¼ in. by 3¾ in.), we
have a balance capable of weighing 3 lb. avoirdupois by thirty-seconds
of an ounce.

For ordinary balances on the torsion system, in which extreme
sensitiveness is not needed, the trouble caused by change of level of
the scale is insignificant; but it becomes a matter of importance in