Encyclopaedia; or, A dictionary of arts, sciences, and miscellaneous literature; constructed on a plan, by which the different sciences and arts are digested into the form of distinct treatises of . al lurface in the circuniferencc of a circledefcribcd by the revolution of the point P roimd the axisRVCF; that is, cf all the rays which occupy the coni-cal lurface defcribed by the revolution (if RP, and the ,refraded rays occupy the conical furface produced bvAthe revolution (fPF. -^ ^ Eut no otlier rays flowing fr&m R are coUeaedf^tF; for it appeared in the demonllrationof that pro-po
Encyclopaedia; or, A dictionary of arts, sciences, and miscellaneous literature; constructed on a plan, by which the different sciences and arts are digested into the form of distinct treatises of . al lurface in the circuniferencc of a circledefcribcd by the revolution of the point P roimd the axisRVCF; that is, cf all the rays which occupy the coni-cal lurface defcribed by the revolution (if RP, and the ,refraded rays occupy the conical furface produced bvAthe revolution (fPF. -^ ^ Eut no otlier rays flowing fr&m R are coUeaedf^tF; for it appeared in the demonllrationof that pro-pofition, that rays incident at a greater diftance iromthe axis ilC were collected at a ptint between Cand F; and then the rays which are incident on thewhole arch PC, or the fpherical furface generated byits levolation round RC, although they all cr. fs theaxis RC, are dtffufed over a certain portion cf it, bywh; has been called the aberration of figure. It iscalled alfo (but improperly) the aberration from tliegcometiical focus, by which is the loiTus of pencil of rays, of which the middlera^ (or axis of the pencil) occupies the lens RC, and fuffers Plate- CCCIjXII. ^/y</.2.
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Keywords: ., bookcentury1700, bookdecade1790, bookidencyclopaedi, bookyear1798
