[ *7 1 
At the bottom of the Looking-GIafs is a Brafs 
Nut or Joint with a hollow Screw, that re¬ 
ceives the Iron male Screw, which goes through 
the Mahogony ; this muft be firft fcrewed in 
before the Brafs Pin is put through the Joint. 
This being done, and the Brafs Circle fattened 
to the Shutter, with the Looking-glafs on the 
Outfide, fcrew the Tube F F covered with 
Black into the Brafs Collar, provided for it in 
the circular Piece of Mahogony: The Lens on 
the Outfide is about twelve inches Focus, 
and a proper diftance for Things that have no 
Life, is commonly at about ten Inches, but 
it muft be fhortened for living Objeds, till they 
can well fuftain the Heat -, therefore pull out 
the Brafs Drawer G to one of the Marks 
made thereon, as you find moft neceflary. 
The Brafs Knob or Button H is the Head of a 
Screw which goes through the Mahogony Piece, 
and has a Communication with the Looking- 
glafs, which by fcrewing or unfcrewing, ele¬ 
vates or deprefies the Glafs to the Altitude and 
Situation of the Sun. This Button ferves alfo for 
a Handle to move round the circular Piece of 
Mahogony to which the Glafs is likewife fixed, 
and by which two Motions the Sun’s Rays are 
thrown in a dired Line through the Tube, and 
form a round Spot of Light on the Screen. 
Things being thus prepared, take the Hollow 
Cylinder N (in Plate i.) and Aide it on the 
Tube K, till the upper Edge is exad with the 
Mark of that Tube, correfponding with the 
Mark or Number of the Magnifier made ufe on, 
which Magnifier muft be fcrewed. on to the End 
of the Cylinder N. Then thruft the Slider (in 
which your Objed is placed) into the Conveni- 
C ency 
