Let a 2 I b (Fig. 172) be the size of a regulating square, found according to the previous rule, the required number of revolutions being

Scrolls At Newel

1 3/4. Divide two adjacent sides, as a 2 and 2 1, into as many equal parts as there are quarters in the number of revolutions, as seven; from those points of division draw lines across the square at right angles to the lines divided; then 1 being the first centre, 2, 3,4, 5, 6, and 7 are the centres for the other quarters, and 8 is the centre for the eye; the heavy lines that determine these centres being each one part less in length than its preceding line.

Fig. 173.