102 M i c r o s c o p i c a l E s s a y s .
m it’s proper fituation, and the objeft ilider between, the plates at
h : adjuft the objea to the focus o f the magnifying lens by the
fcrew b, till the objea appears diflina and clear on the fcreen.
B y moving the internal tube o f the body, the objea. may be
placed at different diftances from the lens which is fixed at A B,
fo as to be fufficiently illuminated, and yet not fcorched by the
fblar rays. 1
A pparatus belonging to the common Solar M icroscope.
Square plate and mirror.
The body, confifling o f two tubes, one within the other.
The fingle microfcope.
The megalafcope lens, Fig. 6.
The Aider, Fig. 8, with fix lenfes.
The two fcrews O, P.
Six ivory Aiders and a talc box.
Some glafs tubes.
A Aider, or brafs cafe, containing a plane piece o f glafs, and a
brafs Aider with holes, into which are cemented fmall concave
glafies, defigned for confining fmall infefts between the plane and
4 concave
M i c r o s c o p i c a l Es s a y s . IC3 .
concave glafs, which are thus preferved from being crufhed, and
prevented from wandering out of the field of view.
T he S crew Barrel, or W ilson’s single Pocket
Microscope, Fig. l and 2, Plate II. B.
This microfcope o f Mr. Wilfon’s is an invention o f many years
ftanding, and was infomemeafure laid afide, till Dr. Lieb_rkuhn
introduced the folar apparatus, to which he applied it, there
being.no other inftrument at that time which would anfwer his
purpofeTo well; fince which time it has been revived, and much
efteemed, though very troublefome in many cafes.
The body of the microfcope is reprefented by A B , Ficr. 1,
and is made either of filver, brafs, or ivory.
c C is a long fine-threaded male fcrew that turns into the
body o f the microfcope.
D, a convex glafs at the end o f the faid fcrew, on which may
be placed, as occafion requires, one o f the two concave pieces o f
thin brafs, with holes o f different diameters in the center of them,
to cover the faid glafs, and thereby diminifii the aperture when
the greateft magnifiers are ufed.‘
E, three thin plates of brafs within the body o f the microfcope.
one whereof is bent femicircularly in the middle, fo as to form
an arched cavity for the reception o f a tube o f glafs.
F, a