American horological journal, devoted to practical horology (1869)
Miller, George B · New York, G. B. Miller · leaf 176
equal to the angle of reflection. Let M N be a very small portion of thecircumference of a circle with its centre at O.Let the line a x, passing through the centre,cut the arc M N into two equal parts at a.Then imagine the curve M N twirled rounda a: as a fixed axis ; the curve would describepart… … The line a xis the principal axis of the mir-ror. All rays from a point placed at the centreO strike the surface of the mirror as perpen-diculars, and after reflection return to O. Aluminous point placed on the axis beyond O,say at x, throws a divergent cone of raysupon the mirror. These rays are…
Clocks and watches
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