C 18 ' 
OPT 
either the nippers ale, fig. 5, or the fifh-pan, fig. 6. when 
thefe are ufed, the Aider-holder mull be removed. A 
hole is made in the oppofite fide of the ftage to receive 
the pin g of the convex lens S, fig. 7. 
To ufe this microfcope: Take it out of the box. Screw 
the body into the round end of the upper part of the arm 
CD. 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, and Aide it forwards until the 
magnifier you mean to ufe is under the centre of the body : 
oppofite to each magnifier in this Ait there is a notch, and 
in the dove-tailed part of the arm CD there is a fpring, 
which falls into the above-mentioned notch, and thus 
makes each magnifier coincide with the centre of the body. 
Pafs the ivory Aider you intend to ufe between the upper 
plates of the Aider-holder KL, and then refledt as ftronga 
light as you can on the objedt by means of one of the 
mirrors; after this, adjuft the objedt to the focus of the 
magnifier and your eye, by turning the milled ferew M, 
the motion of which raifes and deprefies the Aage NIS. 
The degree of light necefiary for each objedt, and the ac¬ 
curacy required in the adjuftment of the lenfes to their 
proper focal diftance from the objedt, will be ealiiy attained 
by a little pradtice. 
When opaque objedts are to be examined, remove the 
Aider-holder, and place the objedt on a fiat glafs, or fix it 
in the nippers, fig. 5. the pin c of thefe fits into the hole 
on the ftage ; ferew the concave fpeculum R into the arm 
Q, fig. 4. and then pafs the pin of this arm through the 
focket D, fig. 3. The light is now to be refiedted from the 
concave mirror to the filver fpeculum, and from this down 
on the objedt. The fpeculum mud be moved lower or 
higher, to fuit the focus of the different magnifiers and 
the nature of the objedt. 
The foregoing diredtions apply equally to the ufing of 
this inftrument as a /ingle microfcope; with this differ¬ 
ence only, that the body AB is then removed, and the 
eye is applied to the upper lurface of the arm CD, exadtly 
over the magnifiers.. 
This microfcope is fometimes made with the following 
alterations , which are fuppofed to render it ftill more con¬ 
venient and ufeful. The arm CD that carries the body 
and magnifiers is made both to turn on a pin, and to Aide 
backwards and forwards in a focket at C ; fo that, in (lead 
of moving the objedts below on the ftage, and difturbing 
them, the magnifiers are more conveniently brought over 
any part of the objedts as defired. The condenfing glafs 
is made larger, and Aides upon the fquare bar CF quite 
dlftindt from the ftage, like the mirrors below ; and it is 
thereby made ufeful for any other objedts that may be 
applied on glafles fitted to the ftage, as well as thofe put 
into the Aider-holder K. It is thereby not confined to 
this ftage alone, as in the preceding. When the body AB 
is taken away, the arm CD may be Aipt away from its 
bar," with the magnifiers, and the forceps, wire, and joint, 
applied to it, as at fig. 5. and it thereby ferves the purpofe 
of a fmall hand tingle or opaque microfcope, for any ob¬ 
jedt occafionally applied to this wire. The magnifiers in 
the Aider E are mounted in a wheel cafe, which perhaps 
prevents its being in the way fo much as the long Aider 
E before deferibed. This contrivance is reprefented at 
fig. 8. and feparated at fig. 9. 
Martin's new univerfal compound microfcope, which com¬ 
bines the ufes and advantages of the fingle, compound, 
opaque, and aquatic, microfcopes, as now conftrudted by 
the opticians of London, is reprefented at fig. 10. A, B, 
D is the body of the microfcope, which confifts of four 
parts; viz. AB the eye-piece, or that containing the eye- 
glaffes, and is ferewed into the top of a movable or Aiding 
tube, which contains the body-glafs ferewed into its lower 
part. D is the exterior tube or cafe, in which the other 
Aides up and down in an eafy and fteady manner. This 
motion of the interior tube is ufeful to increafe or decreafe 
the magnifying power of the body-glafs when thought 
neceffary. E is a pipe or fnout ferewed on to the body 
I c s. 
of the microfcope D, and at its lower part, over the feve- 
ral magnifying tenfes hereafter deferibed. FGHI is the 
fquare ftem of the microfcope, upon which the ftage R 
moves in an horizontal pofition, upward or downward, 
by means of the fine rack-work of teeth and pinion. KL 
is a ftrong folid joint and pillar, by which the pofition of 
the inftrument is readily altered from a vertical one to an 
oblique or to a perfedtly-horizontal one, as may be re¬ 
quired : it is thus well adapted to the eafe of the ob- 
ferver either fitting or {landing ; and, as it is very often 
convenient to view objedts by diredl unrefledted light, 
when the fquare ftem FI is placed in an horizontal pofi¬ 
tion for this purpofe ; the mirror T is then to be taken 
off, in order to prevent the obftrudtion of the rays. NOP, 
the tripod or foot by which the whole body' of the micro¬ 
fcope is fteadily fupported ; thefe three arms fold up under 
each other at N, when packed into the cafe. W is a brafs 
frame that contains the condenfing lens, and adts in con- 
jundtion with the large concave and plane mirrors below 
at T; the refiedted rays from which, either of the com¬ 
mon light or of that of a candle or lamp, it agreeably 
modifies, and makes fteady in the field of view. 
The particulars of the apparatus to this microfcope are 
as follow : Q (fee alfo figs. 8, 9.) is a circular brafs box, 
containing fix magnifiers, or objedt-lenfes, numbered 1, 
2, 3> 4, 5, 6 ; the digits of which appear feverally through 
a fmall round hole y, in the upper plate of it. To 
the upper fide is fixed a fmall circle of brafs z, by 
which it is connedted with, and ferewed into, the round 
end of the arm abc; which is a long piece of brafs, and 
moves through either by teeth or pinion, or not, as may 
be defired, in ef; which is a focket on the upper part of 
the pillar, and admits, with a motion both eafy and fteady', 
the brafs arm. R is a fixed ftage, upon which the objedts 
to be viewed are to be placed : it is firmly fattened to the 
fquare pillar, which is moved by the rack-work. In the 
middle is a large circular hole, for receiving concave 
glaffes, with fluids, &c. it has alfo a Aiding fpring-frame, 
to fallen down flips of glafs or other things : at qtx are 
three fmall fockets or holes, intended to receive i'everal 
parts of the apparatus. S is the refradtor, or illumina¬ 
ting lens, for converging the fun’s rays upon opaque ob¬ 
jedts laid upon the ftage R : or it may be fixed, as in fig. 
7, to move in a femicircle, fixing its long fhank g, in a 
fpring-focket h, in the arm i; this arm moving every 
way by a flout pin k in the focket t of the ftage. In this 
manner it is eafily adjufted to any pofition of the fun, 
candle, See. T, the refledting-glafs frame, containing a 
concave and plane fpeculum, which is moved upon the 
fquare pillar by the hand. The ufe of it is to illumi¬ 
nate all tranfparent objedls that are applied to the ftage 
above. 
Befides the apparatus reprefented, there is an auxiliary 
movable ftage, which, by means of a pin, is placed in 
the hole t of the ftage R, and can be moved in an hori¬ 
zontal direttion over the whole field of the ftage. In 
this ftage, there are three circular holes with firouldered 
bottoms; a large one in the middle, and on each fide a 
fmall one, for the reception of the three following necef¬ 
fary articles : a watch-glafs to be placed in the large hole, 
to hold fluids containing animalcules, See. a circular 
piece of ivory, one fide of which is black, the other white, 
to fupport opaque objedls of different contrafted colours ; 
and circular plane and concave glafles, forextemporaneous 
tranfparent objects. The fame ufq is made of the two 
fmall holes as of the large one, only in a lefs degree, to 
receive fmall concave glafles, plates, Sec. 
L, underneath fig. 6, is the filvered fpeculum, called a 
Lieberhhun, which makes the fingle opaque microfcope, 
by being ferewed to the Aider ale, fig. 10, in room of the 
box of lenfes Q, and the body AE above it. The chief 
ufe of this is to view very fmall objedts ftrongly illumi¬ 
nated near the compounded focus of the mirror T. In 
fig. 5 are the forceps or pliers, for holding fuch kind of 
objedts, and by which they can be applied very readily to 
