GENERAL INDEX. 



Lenses, method of grinding for microscopes . . . 

 Brewster's improvements in .... 



polyzonal, or built of zones . 



parabolic of Newton ..... 



pefucopic, combination of . . . 

 Parker's large one described .... 



sapphire and diamond of Pritchard . . . 



table of their magnifying power . . 

 LESLIE'S hygrometer and photometer described 



differential thermometer .... 



thermometrical hygrometer .... 



photometers ...... 



pyroscope ....... 



Lever, principle of, and description of the several sorts of . 

 . . species of, distinguished according to the place of the 

 fulcrum ......... 



Leydenjar, construction of ..... 



Liyht, different hypotheses concerning its nature 

 .. why its rays are visible in their passage 

 . . refraction of, theory concerning .... 



its effects on the apparent places of the 



stars 



through lenses of various forms . 

 transmission of through a glass prism . * 



. . prismatic colours exist in, and not formed in the me- 

 dium through which it passes ..... 



. . how its rays are refracted to the retina . . 

 . . nature and principles of, and axioms concerning 

 . . rays of, always proceed in straight lines 

 . . experiments on its composition and decomposition . 

 . . homogeneous, method of obtaining . . 



law of its refraction ... 



. . reflexibility of, general laws concerning 

 . . not reflected by infringing upon the solid parts of bodies 

 . . reflected by bodies chiefly of their own colour 

 . . duration of its impression on the eye . . 

 . . Halley's experiments upon in a diving-bell . 

 . . its fits of easy reflection and transmission . . 



. . diffraction of, explained, with experiments . 



dispersive powers of by different bodies, table of 

 . . refraction of through different lenses . 



rays of, their primary colours .... 



their different refrangibilities 

 their interference . . . , . 



, . undulations of, account of that theory . 



its polarity suspected by Newton . , . 



.. electric. [See Electric Light.] 



its influence on magnetism .... 



. . stars and pencils of, exhibited on the passage of the 

 electric fluid from or to a pointed body 

 . . electric, exhibited in the ignition of charcoal, &c., by 

 galvanism ...... 



Lnjhtinntj, 'analogy between it and the electric spark . 

 safeguard for ships and buildings from 

 affects the magnetic needle, and sometimes reverses 

 its polarity ... ..... 



Line of no variation of the compass, traced . 



s, in what they differ from air .... 



v their undulation 



colours vary with their thickness 

 ( may-nets, where found 

 t-n- virtue more tenaciously than artificial 



OPT. INST, 



TJIKUM. 



POP. INT. 



ELECT. 

 POP. INT. 



NEW. OPT. 



OPT. INST. 

 NEW. OPT. 



ELECT. MAON. 



ELECT. 



GALV. 



ELECT. MAC;N. 



M.UiN. 



POP. INT. 

 Ni-:\v. OPT. 



M.UiN. 





ould be armed .... 



, remarks concerning . 



of its discovery .... 



's experiments concerning 



' deviation on account of, observed in 



31 



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. 40 



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. 2024 



2224 



34, 35 



, 74, 75 



77 



85,86 



87 



. 89 

 90 



90 



95 



. 9,11 



11, 12 

 2,3 



26 

 2022 



55 

 . 37 



35 

 . 38 



44 

 . 60 



25 



13,35,40 

 11, 12, &c. 



32 



10 

 . 44 



64 



97,98 

 27 



. 10, 11 



59 



. 59,60 



2 



23 

 1 



. 71 

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. 6168 



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