C 4009 ) 
Js, that all the Seftions parallel to the Axis make the fame Pa^ 
rabola^ 
Thus far M. Bugenius his judicious Letter ^ to the latter part 
of which, concerning the grinding Parabolical Conoids^ Mr. 
NemorriMh^ in his Letter to the Publiflier of Feb. 20, 71. 
that though he with him defpairs of performing that work by 
Geometrical rules, yet he doubts not but that the thing may 
in forae mcafure be accompliflied by Mechanical de* 
vifes. 
To all which I cannot but fubjofin an ExtraB ef a Letter ^ received 
# very lately^ (March 19th) from the Inventor of this mm Te- 
h[c9pe^ /r<?w Cambridge, vii{. 
IN my laft Letter I gave you occafion to fufpeft, that the 
Inftrument which I fent you^ is in fome refpeft or other 
iudifpofed, or that the metals are tarniflied. And by your 
Letter of March 16^ I am fully confirmed in that opinion.For, 
whilefl: I had it^ it reprefented the Moon in fome parts of it as 
diftinftly, as other Telefcopes ufually do which magnifie as 
much as that. Yet I very well know, that that Inftrument 
hath its imperfcftions both in the compofiition of the metallj 
and in its being badly caflt, as you may perceive by a fcabrous 
place near the middle of the metall of it on the poliflied fide, 
and alfo in the figure of that metall near that fcabrous place. 
And in all thofe refpefts that inftrument is capable of further 
improvement* 
You feem to intimate^ that the proportion of 58 to i holds 
only for its magnifying Objefts at fmall diftances* But if for 
iuch diftances, fuppofe 500 feet^ it magnifie at that rate, by 
the rules of Opticks it muft for the greateft diftance imagi^ 
nable magnifie mere than to 1 5 which is fo confiderable 
a diminiftiing , that it may be even then as 58 to i . 
Here is made another Inftrument like the former^ 
which does very welU Yefterday I compared it with a fix 
f oot Telefcope, and found it not only to magnifie more, but 
alfo n^ore diflinftly. And to day I found, that I could read 
j in one of the Philofophical TranfaBions , placed in the Sun's 
LI II 2 lights 
