D is a nut fitted to the faid fcrew, which, when turned, will
either feparate or bring together the two arms A C.
E is a fteel fpring, that feparates the two fides when the nut
is unfcrewed.
F, a piece o f brafs turning round in a focket, whence proceeds
a fpringing tube, moving on a rivet, through which runs a fteel
wire, one- end o f which finifhes in a point G, and the other end
hath a pair o f pliers H foldered to i t ; thefe are either to thruft
into, or to take up and hold any object, and may be turned
round as required.
I, a ring of brals, with a female fcrew fixed on an upright
piece o f the fame metal,, which turns on a rivet, that it may be
fet at a due diftance when the leaft magnifiers are ufed, and
ferves the fcrews of all the magnifiers.
K , a concave fpeculum o f filver, polilhed as bright as poflible,
in the center of which a double convex lens is placed, with a
proper aperture to look through it. On the back of this fpeculum
a male fcrew L is made to fit the brafs ring I, which may be
fcrewed into the faid ring at pleafure.
Four of thefe concave fpecula, of different depths, are fitted to
four glaffes o f different magnifying powers, to be ufed as the ob-
jefts to be examined may require. The greateft magnifiers have
the leaft apertures.
M, a
M, a round objeft plate, one fide white, and the other black,
intended to render objefts the more vifible, by placing them, if
black, upon the white, and if white, on the black fide.
A fteel fpring N turns down on each fide, to make any objeft
f a ll: from the objeft plate there is a hollow pipe, to fcrew it on
the needle’s point G.
O, a fmall box of brafs, with a glafs on each fide, contrived ,
to confine any living objeft in order to examine i t ; this alfo has
a pipe to fcrew upon the end of the needle at G .
P, a turned handle of ivory, to fcrew into the inftrument when
it is made ufe of.
O, a pair o f pliers to take up any objeft, or manage it with
eonveniency.
R, a foft hair brufh, to clean the glaffes or fpecula.
When you would view any objeft, fcrew the fpeculum, with
the magnifier you intend to ufe, into the brafs ring I : place your
objeft either on the needle G, in the pliers H, on the objeft
plate M, or in the brafs hollow box O, as may be moft convenient,
according to the nature and condition of i t ; then holding
up-your inftrument by-the handle P, look againft the light
through the magnifying lens; and by means of the nut D, together
with the motion o f the needle; by managing its lower end,
the objeft may be turned about, raifed or deprefled, brought
nearer the glafs, or put farther from it, till you hit the true focal
diftance,.