To USE THE IMPROVED DOUBLE MICROSCOPE.
Take the microfcope out o f the box. Screw the body into the
round end o f the upper part o f the arm C D.
Place the brafs Aiders, which contain the magnifiers, into the
dove-tailed Ait which is on the under fide of the aforefaid arm, as
feen at E, Fig. i, Plate IV. and Aide it forwards, until the magnifier
you mean to ufe is under the center o f the body : oppofite
to each magnifier in this Aide there is-a notch, and in the dovetailed
part o f the arm C D there is a fpring, which falls into the
above-mentioned notch, and thus makes each magnifier coincide
with the center o f the body.
Pafs the ivory Aider you intend to ufe between the upper
plates o f the Aider-holder K L, and then reflect as Arong a light
as you can on the objefcl, by means of one of the mirrors ; after
this, adjuft the object to the focus of the magnifier and your eye,
by turning the milled fcrew M ; the motion o f this raifes and
deprefies the fiage N I S. The degree of light neceffary for each
object, and the accuracy required in the adjufiment o f the lens
to their proper focal difiance from the object, will be eaffiy
attained by a little practice.
When opake objects are to be examined, remove the Aider-
holder, and place the objeft on a fiat glafs, or fix it to the nippers
L , Plate IX. the pin o f thefe fit into the hole on the fiage;
fcrew the concave fpeculura R, Plate IX. into the arm Q, Plate
4 IX.
IX. and then pafs the pin o f this arm through thefocketD, Fig. 1,
PI. IV. the light is now to be reflefted from the concave mirror to-
the filver fpeculum, and from this down on the objeft. No exadt
rule can be given for reflefting the light on the objeft; we muft
therefore refer the reader to the mother o f all aptnefs, practice.
The fpeculum muft be moved lower or higher, to fuit the focus
o f the different magnifiers, and the nature o f the objeft.
The preceding directions apply equally to the ufing of this in-
ftrument as a single microscope, with this difference only,
that the body A B is then removed, and the eye is applied to the
upper furface of the arm C D, exactly over the magnifiers.
A L ist of the A pparatus of the improved C ompound
Microscope,
The Aider, with the magnifiers.
The body of the microfcope.
The Aider-holder.
The tube, with the condenfing lens.
The pin and arm for the filver fpeculum.
The filver fpeculum.
A brafs box for the filver fpeculum.
A braß