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# Title: Opticks: Or, A Treatise Of The Reflexions, Refractions, Inflexions and Colours Of Light (shelfmark Leibn. Marg. 193)
# Folio 79, page id 1677894601:0089
# Original at the GWLB: https://digitale-sammlungen.gwlb.de/resolve?id=1677894601&page=89
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# Model: FoNDUE-GD_v2_ft_Leibniz, run 74, 2026-09-06T16:05:13Z — 32 lines, status machine
# Lines: 32 recognised, mean confidence 0.90
# Machine transcription. Not an edition. Errors are expected: about 8% character error rate on Latin and French lines, higher on German.
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# After the first blank line: the recognised lines in reading order, one per line.

aL. DII. L+00. Ll.
To sorten Felescopes.
ET ABDC represent a Clals spherically coneare On Fiz. 29.
the Foreside AB, and as much conrex on the back-
Side CD, Po that ic be every irhere ot an equal chicknels. L eF
ic noc be chicker on one side than on the ocher, lest ic make
Objects appear coloured and indictinet, and let it be very
cruly irroushe and quick-silvered overon chebacksde; and
sec inche Tube VXVZ which must be very black rithin.
LeE FFC reprelent a Prism of Clals or Crystal placed near
the ocher end of the Tube, in che middle of ic, by means ot
2handle oF BraIS OF ITON FOK, to che end ot ehich made
Aac ic is cemented. Lec chis Prilm be rectangular aF F, and
lec che ocher erro Anoles at F and O be accurately equal EO
each ocher, and by consequence equalco halt righe ones, and
lec the plane Cides FF and OF be square, and by conse
quence the chird Side FO a rectansular parallelooram, whole
lenseh is eo its breach in a Tubduplicate proportion ot ervo
eo onc. Lec ic bc (0 placed in the Tube, thac che Axis oF
thespeculum may pals chrouoh che midale ot the square
lide F.F perpendiculartr, and by consequence chrouoh the
midele oFche side F C ac an Anele oF 45 deorces, and lec the
Side EF be curned tomards che speculum, and the distance
oFchisPrim Erom che Speculum be such chac che Raysofche
lighc PD RS, _cc. Wrhichare incidene upon the speculum in
Tines Parallel co che Aris chereof may encer che Prism ac
ehe Side FF, and be redlected by che side F G, and chence
50 oue ot ic chrouoh che side CF, to che poine Y itict
must be the common Focusof the Speculum ABDC, and ot
2 Plano- convex Pre- Ola(s FI, chrouch ihich chole RayS
must pals coche Frc. And lec che. Rays at cheir comins
DuF