Dr. Gregory's Elements of catoptrics and dioptrics / Translated from the Latin original, with a large supplement, by William Browne.

Gregory, David, 1659-1708. Catoptricae et dioptricae sphaericae elementa. English

Date:: 1735

Credit: Dr. Gregory's Elements of catoptrics and dioptrics / Translated from the Latin original, with a large supplement, by William Browne. Source: Wellcome Collection.

44/330 page 16

$f ' / < *t . • r. . >•. .... C O R O I,* (]>• A radiant Plane and its Image made by a plane Speculum, are equal and fimilar Figures, but not fimilarly placed. They differ as the Right Hand from the Left, or as a Figure engraven upon a Copper Plate, does from the Impreffion of it taken upon Paper. For they will fit if they come together. CoROt. 5. .. ..... \ . Becaufe the Right Line a B is equal to AB, aO will be equal to AB and BO together,• that is, the Diftance of the Image from the Eye, is equal to the Incident and reflected Ray taken both together. COROL, <5. Whatfoever has been faid of the Image of any Object or primary Radiant, holds true alfo of the Image of another Image. From whence arifes that Multiplication of Images, made by two or more plane Specula duly pofited; in which it is principally to be obferved, that the Diftance of any Image from the Eye, is equal to a Ray propagated from the primary Radiant, thro’ all the in¬ termediate Reflections to the Eye. Lem-$