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52 INSTRUMENTS AND APPLIANCES

after multiplying, cut off two figures (move the decimal point

two figures to the left) as in calculating interest (Fig. 55).

270

180
Fig. 55.—The centigrade circle. 25,
50 and 75 centigrades equal respectively
90, 180 and 270 astronomical degrees.
COMPARISON OF CENTIGRADE ANGLES
WITH ASTRONOMICAL DEGREES
(TABLE FROM BLACK)
6 centigrades 21.6 degrees
12 centigrades 43 • 2 degrees
18 centigrades 64. 8 degrees
23 centigrades 82 8 degrees
.
28 centigrades 100.8 degrees
80 centigrades 288.0 degrees
Q5 centigrades 340.0 degrees

The Dental Instrument Gauge

The millimeter measure and the
centigrade circle have been combined
in an instrument known as the Den-
tal Instrument Gauge. This appli-

ance is largely used by instrument
manufacturers for measuring the
length, width and angle of the cut-
ting edge of the blade and the angles
Fig. 56.—Dental instrument
in the shank of the instrument; but gauge.