( 4^57 ) 
you'I have iefs difficuJty indifcoveringtheObjeds, thaa 10 
that of Mr. Newtmi. 
A 
So far this French Author, To which we Jhall nm fubjoin the 
C onfiaer alien s oj Mr. Newcon^ astve received them from him 
in a Letter, written from Cambridge May ^ih. iSji^as follows, 
SIR 
1 Should be very glad to meet with any improvement of 
the Catadioptrical Telefcope ; but that dtfign of itjwhich 
fas you infbrme mc )Mr, Cajpgrain hath communicated 3 months 
fince, and is now printed in one of the V tench Memoires^ I 
fear will not anfwer Expeftation. For, when I firft applied my- 
felf to try the effcfts of Reflexions^ Mr. Gregorys Optica Pro- 
mota ( printed in the year 1 663 ) being fallen into my hands, 
where there is an Inftrument ( defcribed pag» 94 ) like thac 
of Monfieur CaJJegrain's with a hole in the midftot the Objed:- 
Metal to tranfmit the Light to an Eye-g!afs placed behind it 5 
I had thence an occafion of confidering that fort of conftrufti- 
ons^ and found their difadvantages fo great, that J faw it ne- 
ceflTary," before I attempted any thing in the PracSiquej to al- 
ter the delignof them, and place theEye glafs att^e fide of 
the Tube rather than at the midle* 
The difadvantages of it you will underftand by thefe par??- 
culars. i*There will be more light loft in the Metal by reflexion 
from the little com ^yifpeculum^ than from the Oval plane. For^ 
it is an obvious obfervation, that Light is moftcopioufly tc- 
fleftedfrom anyfubftance when incident moftobliquely.^^The 
convex SpeculumwiW not refled: the rays fo truly as the oval 
plane, unlefs it be of an Hyperbolique figure ^ which is in- 
comparably more difScult to forme than a plane; and if tru- 
R r r r 2 iy 
