( BH7 ) 
cal figurejthe rays, coming from the principal point of the 
objeft to the Eye, woiald more exaftiy meet in one point ac 
the bottom of the l{etina^ and confequently, that from one 
certain point of a determinate diftauce you would more per- 
fedly fee that point 5 yet would not fuch a figure reunite 
the rays of the other lateral points of the object, each ex- 
actly in a point of concourfe in the faid retina^ So thatj if 
the vifible object were nothing but a point, and thefurfaces 
of the Ghryftallin hyperbolical, (which they are not,) there 
would then be made a more exquifite vifion of that oniy 
point. 
The Second part delivers the Theory of the Telefcope 
in all it% kinds : which is uflier'd in by a Hiftory of the 
Invention and Antiquity of Telefcopes 3 and by a Difcourfe 
concerning the Difference of the Ancient Glafles from the 
Modern* 
This done, he explains the matter of this fecondPart in 
XL Sediions. 
1. Shews the power, which diaphanous ;;3/?<3^//:^;?2'i'5 lefs fub- 
tile then Air, and of figures fimply Spherical, have in re* 
frad:ing the vifual rays paffing thorow them* 
2. Declares the EfFecSts of Spherical Convex Glafles, to 
ferve for the conftruition of the Telefcope of the firfl kindj 
which always fuppofeth the Eye between the Glafs , and its 
point of Concourfe. 
5. Confiders the AfFedions of Spherical Concaves,to ferve 
for the conftrudion of the fame kind of Telefcope. 
4. Demonftrates the Fffedts of the Conjundion- of Spheri* 
cal Convexes and Concaves,in the Conftrudion of the fame 
fort of Telefcope, 
5. Examins the AfTedions of Spherical Convexes , in the 
Conftrudion of a Telefcope of the fecond kind ; wherein the 
Eye is always more dilfeant from the Convex Objeftive 
Glafs , than its point of Concourfe , andT^ich admits no 
Concave^ 
6^ Shews the EfFeds of the Compofitionor Multiplication- 
of Spherical ConvexeSjin the confl:r:U(aion of all for.ts of Telef- 
copes of the fecond ioiu j.De- 
