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# Title: Opticks: Or, A Treatise Of The Reflexions, Refractions, Inflexions and Colours Of Light (shelfmark Leibn. Marg. 193)
# Folio 59, page id 1677894601:0069
# Original at the GWLB: https://digitale-sammlungen.gwlb.de/resolve?id=1677894601&page=69
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(59
50 chen, il che ratio oF che sines of Incidence and Re-
traction otany Pore of Rays be Found in any onc Cale, tis
siren in all Cales; and chis mar be readily found by che
Mechod in che Follorrine Propolition.
PROF. VII. THCO. VI.
The Perfection of Tele scopes is impeded by the different Refran-
sibilitys of the Rays of Light.
FTF imporfection oF Velelcopes is milgarty accri-
buced co che spherical Figures oF che Glastes, and
cheretore Machematicians hare propounded to Figure them
by che Conical Sections. Fo Chew chat chey are milta-
ken, Phare inserced this Propolition; the cruth of which
will appear by che meatures oFche Retractions oF che sere-
ral POres OF Rays; and chele meatures l thus determine.
in che chird experiment oFche Arst BOOk, Wrhere che re-
tractins Anole ot che Prism was 62 deorees, che halt ot
chac Angle 31 de8. 15 min. is che Angle ot Incidence ot
che Rays at cheir goins our ofche Clals inco the Air; and
the sine oF this Anole is 5188, che Radius being 10000.
When che Axis oF chis Prilm was parallel to che HIOrizOn,
and che Retraction oF che Rays ac their Incidence on chis
Prism equal to chac ac cheir Pmergence ouc of ic, l oblerred
wicha Guadran the Ansle which che mean retrangible Ray5
(thacis, cholewhich enero che midele otchesuns colour-
ed Imase) made wich cheHorizon and by chis Angle and
che suns alcicude obserred at che lame time, PFound che
Angle which che emersent Rays contained wich che incidenc
cobe 44 deg. and 10 min. and chehals of chis Angle ad-
ded co che Angle ol Incidence 31 des. 15 min. makces che
Angle