The description and use of a joynt-rule fitted with lines for the finding the hour of the day and azimuth of the sun, to any particular latitude, or, to apply the same generally to any latitude : together with all the uses of Gunters quadrant applyed thereunto ...
Brown, John, philomath.
The use of the line to divide a circle into any number of parts.
Take the Semidiameter, or Radius of the circle between your compasses, and fit it over in six and six of the line of circles, then what number of parts you would have, take off from that point by the figure in the line of circles, and it shall divide the circle Page [unnumbered]
[illustration]
Page [unnumbered]
Page 109
into so many parts. As suppose I
would have the former circle divided
into nine parts, take the measure
from the center to the circle as exact∣ly
as you can, fit that over in 6 and 6,
then take out 9 and 9, and that shall
divide it into so many parts; but if
you would divide a wheel into any
odde parts, as 55. 63. or 49 parts,
you shall finde it an almost impossible
thing, to take a part so exact that in
turning about so many times, shall
not miss at last: to help which the parts
the rule giveth shall fit you exact
enough for all the odde parts, then
the even will easie be had by dividing,
therefore usually the rule is divided
but to 30 or 40 parts. So that for this
use as the finding the side of an 8 or
10 square piece, as the mast of a ship,
or a newel, or a post, this will very
readily, and exactly help you.
