( ^o6) 
Difli, I, to receive the Ball of the Eye, and guard it 
from external Light, 
On the Top of the Tube is fix’d, on two final! Pede- 
ftals, a common Dioptrick Telefcope, H, Fig, i, about 
cighteeen Inches long, its Axis parallel to that of the 
Tube ^ and having two Hairs plac’d in the common 
Focus of its Objed and Eye-GlalTes, crofling one an- 
other in its Axis, 
There are three convex Eye-Glafies belonging to the 
Inflrument, The firft, or fhalloweft, has its focal Di- 
ftance of about j of an Inch , the fecond, of -A •, and 
the deepeft, of or fomething lefs. When the firft 
of thefe is ufed with the Inftrument, it magnifies about 
1 88, or 190 times, in Diameter ^ with the fecond, about 
208 ; and with the third, 228 or 230. Each of thefe 
GlalTes has placed, in that Focus neareft the Oval, a 
Circle to determine the Part of the Objed feen at one 
View^ and in the other Focus toward the Eye, a Brafe 
Plate with a little Hole in the middle, to let no Light 
pafs to the Eye from the Infide of the Tube, but what 
comes from the Oval. Befides thefe three convex, there 
are two concave E}^e-Glaires, with which it magnifies 
about 200 and 220 times ^ and alfo a Sett of three 
. Convex, which turn it into a Day Telefcope, magni- 
fying about JL25 times. The Aperture is limited by a 
Circle of Card, or Paftboard, placed before the Ob- 
jed-Metal in the Tube. To vary the Aperture there 
are three of thefe Circles, and the Apertures allowed 
by them are five Inches and an half, five Inches, and 
four and an half, tho’ for fome Objeds the whole Me- 
tal may be left open. 
The Engine made ufe of to dired the Tube to any 
Objed, confifts of a ftrong Plank, FF, Fig, i.and^. 
about fourteen Inches wide, and two Feet and an half, 
or three Feet long, which ferves as a Foundation for 
the 
