18 ^The Double ReJleBing Microfcope . 
may be examined fucceffively with very lit¬ 
tle Trouble. 
is a concave Looking-glafs, fet in a 
Box of Brafs, and turning in an Arch R. 
upon two fmall Screws ss. From the Bot¬ 
tom of the Arch comes a Pin, which, be¬ 
ing let down into a Hole t 9 in the Center 
of the Pedeftal, enables the Looking-glafs to 
turn vertically, or horizontally, and reded; 
the Light, either of a Candle, or the Sky, 
diredly upwards on theObjed to be viewed. 
V. is a plano-convex Lens, which by 
turning on two Screws when the Pin at 
the Bottom of it is placed, the Hole W. for 
its Reception in the circular Plate L. will 
tranfmit the Light of a Candle, to illuminate 
any opake Gbjed that is put on the round 
Piece of Ivory, or on the Ebony, for Exami¬ 
nation : and it may be moved higher or low¬ 
er as the Light requires. This Glafs is of 
good Service to point the Sunihine, or the 
Light of a Candle, upon any opake Gbjed ; 
but in plain Day-light it is of no great' Ufe. 
X. a Cone of black Ivory, to fallen on a 
Shank underneath the Brafs circular Plate 
L. principally, when the frit or fecond 
Magnifier is made ufe of, and the Gbjed 
very tranfparent: for Experience teaches, 
that fuch Objeds are rendered much more 
didindly viiibie, by intercepting fame Part 
of the oblique Rays refieded from the con¬ 
cave Looking-glafs, 
The 
J 
