of the 
bigger. 
xiinkis asirnaii again, as that of the Screw of the other two Thirds. 
To the grower Screw is adapted a Socket (f) faftned to a long 
$arr or Bolt (gg r ) upon which is faftned the Moveable Sight {h[) 
fo that every turn of the Screw promotes the Sight Qh ) either a 
tbredn?mr y or a thred farther off from the fixt Sight (i ) The 
Barr (gg) is made exa&lv equal and ft tted into two fmall 5 tables 
{ k k y which will not admit of any (baking. There are 60 of thefe 
threds $ and, anfwerable thereto, are made 6d divifions on the 
edge of the Bolt or Ruler ( gg ) and a fmall Index ( /) fixt to the 
Boxe (a a a} denotes, how many thredsthe Edges of the two 
Sights ( by and ( O are diftant 5 and the Index (et) ftiews on 
the Circular Plate, what part of a revolution there is more •, every 
revolution, aswasfaid before, being divided into ico parts. At 
the fame time that th e moveable Sight (h ) is moved forwards or 
backwards, or more threds of the Courfer Screw, is the Plate 
(ppJnFig.2.) by the means of the Socket ( #) to which it is 
fcrew’d, moved forward or backward 3 or more threds of the fiver 
Screw : 5 So that this Plate , being fixt to the Teleficope by the 
Screws (rr.i n Fig, 2 , ) fo as the middle betwixt the Sights may 
lye in the Axis of the Gla[s y however the Screw be turn’d , the 
midft betwixt the Sights will always he in the Axis , and the Sights 
will equally either Open from it, or (hut towards it. 
Figure 2. reprefents the moveable Cover containing the Screws , 
to be by the Bookfeller cut off, by the pricked Line ( xxx) from 
the Paper, and to be fitly placed on Figure 1. according to the 
pricked Line (yyy [) anfwering thereto* that by the taking off, 
as it were, or folding up of this Cover , the inward contrivance 
of the Screws and Sights may appear. 
And becaufe it is conceived by forne ingenious men, that it will 
be more convenient, inftead of the Edges of the two Sights 
( h and i ) to employ two Sights fitted with hairs, therefore is add- 
ed Figure 3, reprefenting the two Sights (r. andO fo fitted 
with threds ( t. and u . ) that they may be conveniently us’d in the 
place of the [olid Edges of the Sights ( h, and i . ) 
The 4 th Figure reprefents, How th e Screws are to be put on, 
Kkk 2 The 
other m- Thirds of % by at leaft as much $s 
XatMtamade on it: The thred of the Screw of the 
