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 . p!ano-cnvex glafs V^tfAB, into feveial lurfaces, ishb, bid, di. An^CtLXtVobieil C will n^t appear maarnified wlsen feen „, this glafs by the ey; at H; but it will appear multiplied „^ „f ,(,5into as may diiftrent objeifls as the glafs contains furfaces. For, fince rays will flow from the C to all parts of the glafs, and each plane fur-face
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 . p!ano-cnvex glafs V^tfAB, into feveial lurfaces, ishb, bid, di. An^CtLXtVobieil C will n^t appear maarnified wlsen feen „, this glafs by the ey; at H; but it will appear multiplied „^ „f ,(,5into as may diiftrent objeifls as the glafs contains furfaces. For, fince rays will flow from the C to all parts of the glafs, and each plane fur-face will refraft thefe rays to the eye, the lame appear to the eye in the diredlion of the rayswhich enter it through each fnrface. Thus, a rayff;H, falling perpendicidarly on the middle fiirf^ace,will go through the glafs to tlie eye without fulferingany refraiflion; and will therefore fhow the objefl inits true place at C : whilil a ray a b flowing fromthe fame objeifl, and falling obliquely on the planefurface b h, will be refrafled in the dirtilion bf, bypafTirg through the glafs; and, upon leaving it, willgo on to the eye in the dire<5tion * H j which will caitfe Plate Part I r. O V caufc the fime objeA C to appear alfu at E, in thedirection of the ray He, produced in the right linelien. And the ray c J, flowing frvm the objcd C,and falling oblic]ucly on tlie pLiue lurlace <ii, will berelVaftcd, (by paflin;,; through the , and havingit atyV to the eye at H ; \\hicL will caufc tlie fame<jl)jeil to appear at D, in the dirtiftion Ylfni.—Ifthe glafs be turned round the line_^/H, as an axis,the objc(fl: C will keep its place, bccaufe the furfacehid is not removed; but all the other objefls willieem to go round C, bee irfe oblique planes, onwhich the rays abed full, will go round by the turn-ins of the clafs. Plate CCCLXIV. § Mi, It has been elfewherc oUferved, that of mirrorsthere are three principally ufed in optical experiments(
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Keywords: ., bookcentury1700, bookdecade1790, bookidencyclopaedi, bookyear1798
