=604. Ellipsograph;= by gearing; the bevil wheel ~A~ is fixed, the other
three revolving with the whole machine on the fixed central standard,
the distance ~A′~ should equal the difference between the major and
minor axes of the ellipse.
=605. Performs the same operation= in a similar way; ~A~ is fixed; ~B~
is same diameter as ~A~; and ~C~ = ¹⁄₂ diameter of ~A~ and ~B~.
=606. Common trammel or ellipsograph.=
There are other forms of apparatus for _drawing_ ellipses merely (see
Knight’s Dictionary of Mechanics). See Trammel Gear, Sec. 40.
=607 & 608. Two forms of ellipsographs= or elliptical cranks.
See also No. 144.
[Illustration: 594.-608.]