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yiii. Jn Account of a Catadioptrick^ TelefcopCy made 
by John Hadley, F. 5^. S. With the 2)e- 
fcription of a Machine contriv'd by him for the 
applying it to ufe. 
T he Inftrument confifts of a metalline Speculum, 
about fix Inches in Diameter. The RaJius of 
the Sphere, on which its cone ive Surface was ground, 
is ten Feet, five Inches and one quarter, and confequent- 
ly its focal Length is 62 i Inches. The Back has a 
hollow Screw made at its Centre, to receive the End of 
a Handle, which is ferew’d on, whenever the Metal is 
to be moved, in order' to avoid fullying its polilh’d Sur- 
face by handling. 
This Objed-Metal A, PL WFig, i. is placed in one 
End of an odangular Tube, B B, about fix Feet long, and 
fomething wider than what is fufficient to receive the 
Metal, dyed black on the Infide. About fix or feven ^ 
Inches in -Length of the three uppermofl Sides of the 
Tube C, (toward thatEnd, at which the Metal is plac’d) 
are feparated from the reft, and open with two Hinges, 
to make room for the Metal to be put in and taken out. 
The End of the Tube is clofed by an odangular Piece 
of Board D, which has an opening d, about 1 of an Inch 
broad, from the Top down to a little bel )w the Centre, 
to giv^e room for the beforemention’d Handle, when 
the Objed-Metal is lifted into or out of the Tubc^ at 
Other times it is clofed with a Aiding Shutter. The 
B b b 2 Metal 
