Draw a -b equal in height to the largest radius required or given ; number this r. At right angles, draw a -c at any convenient length ; join b-c. We have next to decide how many centres to use ; this is a matter of judgment and depends upon the size of the scroll. In the example, ten has been chosen. Then divide a-h into ten equal parts ; at the eighth part draw a line parallel to a-c, intersecting b- c in X; draw a perpendicular to a-c from this point, which gives No. 2 radius. Next join point 8 to c, and where this line intersects radius 2, draw a similar horizontal to the first, and so obtain radius 3; proceed in like manner to the tenth. We have now a series of radii reduced in geometrical progression. To use them, take radius Xo. 1 in the compasses and describe a quadrant as in Fig. 8. Draw lines from the centre at right angles to each other, and upon the one at which the arc finishes set off the second radius, marked centre 2. measuring from the circumference. Describe a quadrant with this, o.nd proceed in like manner with the remaining radii. The scroll might be continued until it finished into the " eye " or point, but to do so would hide some of the centres and make the drawing less clear.
In Fig. 8 the numbers are placed close to the centres from which the radii spring, and they read towards the radii they refer to.
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