Opticks 1717 - Up

[ 281 ]
.$er ,cl~it of doubt, I added the follownng Q&.
Jkwtiont ’
Oh/’ 2. If thefe Rin~gs thus depend. on the
~h~ch~f s of the Plate it Glad, their Diameters
it equal difkmces from k&al Speculun~s made
-of fuch cOnCaVO-ConBeS; Plates of GInis as arc
ground on the C~rnk Sphere, buglft to be reci-
@ocally in a ii+duplicate proportion of the
~hickneffes of the Plates of Gla&. ‘>?and if this
~rOpO~fiOl1 be found twe~ by cxpcrience it will
pmunt to a demonl’rrntion that thek Rings i
/like thofe formed in thin Plates j do depend
on the thiclcncfs of the Glak, I procured tjlerc-
Ifclre another concave -convex Hate of Gfafi
ground 911 both iides to the fkne Sphere witfl
the former Plate. Its thicl;~.~eils was 7;7 pa-ts of
.?ll Inch ; and the Digmetcrs of the three firit
bright: 1G.1gs mea&red bdtween the brighreit
jmts of their Orbits, at the diikmce of j‘i.x Feet
from the Glafs WCK 3. 4-k 5;. Inches. Now
the thiclinefs of the other Glafs being G of an
Inch was to the thickn& of this GM as 3 to&,
phat is as 31 to 10, or ~IOOOOOOO to I~OOOOOOO
and the I$.oots of thek Numbers are 17607 and
. $0000, and in the proportion of the firit of
Fhefe Roots to the fecond are the Kkuneters of
the bright: Kings made in this Obkrvation by
the thinney Glai’s, 3. .4$. 5-& to the Diameters of
the fame I+$ mad& in the third of thefe Objkrvations
by the thicker *Slais I+$. 2;. 2-k+, that:
is, the Diameters of the-Rings are recipr?cally
in a Cubduplicate proportion of the thickneilks
>f the Plates of Glafs.
1 SO thcii. in Plate’s bf Glafs which are alike
con-