CHAPTER XX.
ODDS AND ENDS.
272. Graduated Circles. Fig. 123. For compasses ([App. 67]), and for use in connection with tangent galvanometers ([App. 116]), a graduated circle is necessary. Fig. 123 is a reduced drawing from an original that is 4 in. in diameter. The long lines are 10 degrees apart, the smallest divisions shown being 5 degrees apart. Single degrees can be determined with considerable accuracy with the eye.
Fig. 123.
To divide the circle. Divide the circumference into 4 equal parts; these will be 90 degrees from each other, there being 360 degrees in every circle. Divide each quarter into nine equal parts with a pair of dividers; these will be for the long lines, 10 degrees apart. Divide each of these into two equal parts. If you are used to drawing, you can divide the circle still more, but 5–degree divisions will do.