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... regular helix lies on a circular cylinder. Let a be the radius of the circle thus formed by the axis of the closed helix ; let r denote the radius of the cross section of the ideal toroid on the surface of which the helix lies, supposed small in comparison...
Philosophical Magazine - Page 102
1880

Proceedings, Volume 9

...revolution of a circle round any line in its plane not cutting it. Any simple on a circular cylinder. Let a be the radius of the circle thus formed by the...to the normal section of the toroid. We have 2ira a ., tan 6 5=^-= — N.2irr because -=^- is as it were the step of the screw, and 2irr is the circumference...

Proceedings of the Royal Society of Edinburgh, Volume 9

...helix, because it lies on a toroid * just as the common regular helix lies on a circular cylinder. Let a be the radius of the circle thus formed by the...supposed small in comparison with a; and let 6 denote the iaclination of the helix to the normal section of the toroid. We have 2ira a tan 6 = N.27rr Nr ' because...