( 4m ) 
Jfi Aecmpt &f a New Catsdioptrical Tekfc&pe invinud by Mr. 
Newton, FelldV0 of the j^.Societyj and fnfeQQT th§ M^-- 
thematiques in thi Vmverjiiy of C^mkridgi^ 
* ' \ 
'^T^His Excelleot Mathematician having given us, in th@ 
TraDfa<9:ions of February laft^ an account of the caufe, 
which induced him t© think upon ^jieUing Telefcopes ^ in- 
ftead of B^efmUing ones^ hath the^reupon prefented the Cu* 
rious World with an EJfay of what may be performed by 
foch Telefcopes 5 by which it is found , that Telefcopical 
Tubes may be cpnfiderably Ihortned without prejudice 
to their magnifying efFedl. 
This new inftrument is compofed of two Meta!liny^^^«- 
lurfis ^ the one Concave^ (inftead of an Objedi-glafs) the 
other Plain j and aifo of a fmall plano-convex Eye* 
Glafs. 
By tjgWB I. of tab. !♦ the ftrofturc of it may be eafily 
imagined ; viz. That the Tube of this Telefcope is open at 
the end which refpeCls the objed: j that the other end is clofe, 
w'here the faid Concave is laid, andif^^^ near the open end 
there is a flat OY^lJpeeulum^mzdQ as fmalias may be^the lefs to 
Gbfl:rU(St the entrance of the rays of ILight, and inclined to* 
wards the tapper part of the Tube, where is a little hole fur- 
nifh't with the faid Eye- glafs. So that the rays coming from 
the objea, do firft fall on the Concave placed at the bot* 
tome of the iTube 5 and are thence refledred toward the o^ 
ther end of it, where they meet with the flat fpecujum, ob* 
liquity pofited, by the refledion of which they are dircAed 
to the little plano-convex Glafs , and fo to the fpedators 
Eyes who looking downwards fees the Objed, which the 
Tclefcope is turned to*. 
To under^a^nd this more diftindly and fully, the Readier 
may plcafe to look upon the faid F/^afr^, in which 
A B is the Concave fpemlum^ of which the mdius or fcmi^- 
diameteris i2|or 15 inches* 
C D another metalline fpemlum^^ mhok furface is flat, aid 
the circumference oval 
