OPTICS. 
Aiders are to be placed. L, a part, of the microfcope con¬ 
taining a wire fpiral fpring, keeping the tube QM with 
its plates firm againft the fixed part IK of the fecond 
tube. EF is the 1 'mall rack-work of teeth and pinion, by 
which the tube IG is moved gradually to or from the end 
AB, for adjufting the objects exaftly to the focus of dif¬ 
ferent lengths. NO is a bral's Aider, with fix magnifiers; 
any one of which may eafily be placed before the objeft. 
It is known when either of the glaffes is in the centre of 
the eye-hole, by a fmall fpring falling into a notch in the 
fide of the Aider, made againft each of the.glaffes. 1 hole 
parts of the apparatus before d.efcribed, viz. Aiders, glafs 
tubes, forceps, Lieberkuhns, &c. &c. are made ufe of to 
this microfcope. GH is a brafs cell, which holds an illu¬ 
minating glafs for converging the fun’s beams or the light 
of a candle ftrongly upon the objefts. The aperture of 
the glafs is made greater or lefs, by two circular pieces of 
brafs, with holes of different fizes, that are fcrewed fiepa- 
rately over the faid lens. But, at times, objefts appear 
heft, when the microfcope is held up to the common light 
only, without this glafs. It is alfo taken away when the 
microfcope is applied to the apparatus now to be de-‘ 
fcribed. 
Fig. a. reprefents the apparatus, with the fingle micro¬ 
fcope fcrewed to it, which conftitutes th e folar microfcope. 
AB is the inner movable tube, to which the fingle mi¬ 
crofcope is fcrewed. CD is the external tube, containing 
a condenfing convex glafs at the end D, and is fcrewed 
into the plate EF, which is cut with teeth at its circum¬ 
ference, and moved by the pinion I, that is fixed with the 
plate GH. This plate is fcrewed faft againft the window- 
fhutter, or board fitted to a convenient window of a dark¬ 
ened room, when the inftrument is ufed. KL is a long 
.frame, fixed to the circular plate EF, containing a look- 
ing-glafs or mirror for reflecting the folar rays through the 
lens in the body of the tube D. O is a brafs milled head, 
faftened to a worm or endlefs fcrew ; which on the outfide 
turns a fmall wheel, by which the reflecting mirror M is 
moved upwards or downwards. 
In ufing this microfcope, the fquare frame GFI is firft 
to be fcrewed to the window-fliutter, and the room well 
darkened : which is belt done, by cutting a round hole of 
thefizeof the movable plate EF, that carries the refleftor, 
in the window-fliutter or board; and, by means of two 
brafs nuts a, a, let into the flutter to receive the fcrews 
p P, when placed through the holes in the fquare frame 
GH, at the two holes Q, Q ; which will firmly faften the 
microfcope to the fliutter, and is eafily taken away by only 
unfcrewing the fcrews P, P. 
A white paper fcreen, or white cloth, to receive the 
images, is to be placed feveral feet diftant from the win¬ 
dow : which will make the reprefentations the larger in 
proportion to the diftanee. The ufual diftances are from 
fix to fixteen feet. 
The frame KL, with its mirror M, is to be moved by 
turning the pinion I one way or the other, till the beams 
of the fun’s light come through the hole into the room : 
then, by turning the worm at O, the mirror mult be 
raifed or depreffed, till the rays become perfectly hori¬ 
zontal, and go ftraight acrofs the room to the fcreen. 
The tube CD, with its lens at D, is now to be fcrewed 
into the hole of the circular plate EF: by this glafs the 
rays will be converged to a focus; and from thence pro¬ 
ceed diverging to the fcreen, and there make a large circle 
of light. The fingle microfcope, fig. 7. is to be fcrewed on 
to the end AB, fig. 8. of the inner tube ; and the Aider 
NO, with either of thelenfes marked 1, z, 3, 4, 5, or 6, in 
the centre of the hole at the end AB. This wiil occafion 
a circle of light upon the fcreen much larger than before. 
The Aider or glafs tube, with the objefts to be viewed, is 
to be placed between the plates at IK againft the fmall 
magnifier, and moved at pleafure. By flrifting the tube 
AB in or out, you may place the objeft in fuch a part of 
the condenfed rays as ftiall be fufficient to illuminate if, 
and not fcorch or burn it 5 which will generally require 
Vql. XVII. No. 1203 . 
621 
the glafs to be about one inch diftant from the focus. It 
now remains only to adjuft the object, or to bring it fo near 
to the magnifier, that its image formed upon the fcreen 
fliall be the molt diftinft or p erf eft : and it is effefted by 
gently turning the pinion F, fig. 7. a fmall matter one way 
or the other. If the objeft be rather large in fize, the leaft 
magnifiers are generally ufed, and vice vcrfa. N° 1. is the 
greateft magnifier, and N° 6. the leaft, in the brafs Aider 
NO. But, ifdefired, fingle lenfes of greater magnifying 
powers are made : and they are applied, by being fcrewed 
to the end AB, and the brafs Aider NO is then taken 
away. The fame objeft may be varioufly magnified, by 
the lenfes feverally applied to it; and the degree of mag¬ 
nifying power is eafily known by this rule : As the dijlanccs 
of the objedt is to that of its image from the magnifier; fo is 
the length or breadth of the object to that of the image. In- 
ftead of the brafs Aiders with the lenfes NO, there is fome- 
times fcrewed a lens of a large fize, and longer focal dif- 
tance : the inftrument is then converted into a megalaj'cope; 
and is adapted for viewing the larger kind of objefts con¬ 
tained in larger Aiders. And, in the lame manner, fmall 
objefts of entertainment, painted upon glafs like the 
Aiders of a magic lantern, are much magnified, and re- 
prefented upon the fame fcreen. 
Lucernal (or Camera-obfcura) Tiller of copes, for reprefent- 
ing Opaque Obje£ts .— The great facility with which objefts 
can be reprefented on paper orja rough glafs in the camera- 
obfcura, and copies drawn from them by any perlon though 
unfkilled in drawing, evidently fuggefted the application 
of the microfcope to this inftrument. The greateft num¬ 
ber of experiments that appear to have been made with 
this view, were by Mr. Martin and Mr. Adams ; the for¬ 
mer of whom frequently applied the microfcope to the 
portable camera, and with much efteft and entertainment. 
But thefe inftruments being found to anfwer only with 
the afliftance of the fun, Mr. Adams directed his experi¬ 
ments to the conftruftion of an inftrument of more ex¬ 
tended utility, which could be equally employed in the 
day-time and by night. He accordingly fucceeded fo far 
as to produce, by candle-light, the images of objefts 
refrafted from a fingle magnifier upon one or two large 
convex lenfes (of about five inches or upwards in dia¬ 
meter), at the end of a pyramidal-fliaped box, in a very 
pleafing and magnified appearance, fo as to give opaque 
objefts as well as tranfparent ones the utmoft diftinftnefs 
of reprefentation ; but Hill the light of a candle or lamp 
was found generally infuffleient to throw the requilite 
degree of illumination upon the objefts. The invention 
of what is called Argaud's lamp, within thefe few years, 
offered a complete remedy for this defeft, by the intenfity 
and fteadinefs of its light. This did not efcape Mr. 
Adams (fon of the former), who immediately applied it; 
and who had likewile fo altered and improved his father’s 
inftrument, both in conftruftion and form, as to render it 
altogether a different one, and far more perfect and 
ufeful. 
The advantages and properties of this excellently-con¬ 
ceived inftrument are numerous and important. “ As the 
far greater part of the objefts which furround us are 
opaque, (fays Mr. A.) and very few are fufficiently tranf¬ 
parent to be examined by the common microfcopes, an 
inftrument that could be readily applied to the examin¬ 
ation of opaque objefts has always been a defideratum. 
Even in the examination of tranfparent objefts, many of 
the fine and more curious portions are loft, and drowned, 
as it were, in the light which muft be tranfmitted through 
them; while different parts of the fame objeft appear only 
as dark lines or fpots, becaufe they are fo opaque as not 
to permit any light to pafs through them. Thefe diffi¬ 
culties, as well as many more, are obviated in the lucernal 
microfcope; by which opaque objefts of various fizes may 
be feen with eafe and diftinftnefs; the beautiful colours 
with which mod of them are adorned, are rendered more 
brilliant, without changing in the leaft the real tint of the 
colour 5 and the concave and convex parts retain alfo their 
7 T proper 
