( 3 ^? ) 
fliall be difcovered, ’tis not to be doubted, but that 
the old Dioptrkk Telefcope will be for the moft Part 
laid by, and this Catoptrick one will be chiefly in ufe 
among the pradical Aftronomers , inafmuch as feveral 
Inconveniencies and Difficulties, which are unavoida- 
ble in the Management of the former, efpeciaily when 
long, are in this latter wholly avoided. 
It is no fmall Convenience, that by means of one 
of thefe reflefting Telefcopes, whofe Length' exceeds 
not five Feet, (and which may be managed at a Win- 
dow within the Houfe) Cceleftial Objeds appear as 
much magnified, and as diftind, as they do through 
the common Telefcope, of more than loo Feet in 
Length. 
Mr. Bradley^ the Savilian Profelfor of Aflronomy, 
and myfelf, have compared Mr. Hadlefs Telefcope (in 
which the focal Length of the Objed Metal is not 
quite 5 Feet and i) with the Hugenian Telefcope, the 
focal Length of whofe Objed Glafs is 123 Feet; And 
we find, that the former will bear fuch a Charge, as 
to make it magnify the Cbjed as many Times as the 
latter with its due Charge^ and that it repreieiits Objeds 
as diftind, though not altogether fo clear and bright 
which may be occafioned partly- from -the Difference 
of their iVpertures (that of the Hugenian being fome- 
what the larger) and partly from feveral little Spots in 
the concave Surface of the Objed Metal, which did 
not admit of a good Polifti. 
Notwithftanding this Difference in the Brightnefs 
of the Objeds, we were able, with this refieding Te- 
Jefcope, to fee whatever we have hitherto difcovered by 
the Hitgenian-^ particularly the Tranfits of Jupiter's 
Satellites, and their Shades, over the Dilk of Jupiter \ 
the black Lift in Saturn s Ring , and the Edge of the 
Shade 
