Imágenes de páginas
PDF
EPUB

micro- them as you move it in or out. A few turns of the 2. Single Microscope by reflection. In fig. 2. A is a Microscope. screw CC will easily prevent this mischief, by giving scroll of brass fixed upright upon a round wooden scope.

them room enough. You may change the objects in base B, or a mahogany drawer or case, so as to stand
your sliders for any others you think proper

, by taking perfectly firm and steady. C is a brass screw, that pas-
out the brass rings with the point of a penknife ; ses through a hole in the upper limb of the scroll in-
the talcs will then fall out, if you but turn the sliders ; a to the side of the microscope D, and screws it fast to
and after patting what you please between them, by the said scroll. E is a concave speculum set in a
replacing the brass rings you will fasten them as they box of brass, which bangs in the arch G by two small
were before. It is proper to have some sliders furnish screws fif, that screw into the opposite sides thereof.
ed with talcs, but without any object between them, At the bottom of this arch is a pin of the same metal,
to be always in readiness for the examination of fluids, exactly fitted to a hole h in the wooden pedestal, made
salts, sands, powders, the farina of flowers, or any for the reception of the pin. As the arch turns on
other casual objects of such sort as need only be applied this pin, and the speculum turns on the end of the
to the outside of the talc.

arch, it may, by this twofold motion, be easily adjustThe circulation of the blood may be easiest seen in ed in such a manner as to reflect the light of the sun, the tails or fins of fishes, in the fine membranes be of the sky, or of a candle, directly upwards through tween a frog's toes, or best of all in the tail of a the microscope that is fixed perpendicularly over it ; water-newt. If your object be a small fish, place it and by

and by so doing may be made to answer many purwithin the tube N, and spread its tail or fin along the poses of the large double reflecting microscope. The side thereof: if a frog, choose such a one as can but body of the microscope may also be fixed horizonjust be got into your tube ; and, with a pen, or small tally, and objects viewed in that position by any light stick, expand the transparent membrane between the you choose ; which is an advantage the common double toes of the frog's bind foot as much as you can. When reflecting microscope bas not. It may also be renderyour object is so adjusted that no part of it can inter ed further useful by means of a slip of glass ; one end cept the light from the place you intend to view, un of which being thrust through between the plates where screw the long screw CC, and thrust your tube into the sliders go, and the other extending to some distance, the arched cavity, quite through the body of the mi such objects may be placed thereon as cannot be apcroscope ; then screw it to the true focal distance, and plied in the sliders : and then, baving a limb of brass you will see the blood passing along its vessels with a that may fasten to the body of the microscope, and exrapid motion, and in a most surprising manner.

tend over the projecting glass a hollow ring wherein
The third or fourth magnifiers may be used for to screw the magnifiers, all sorts of subjects may be
frogs or fishes : but for the tails of water-newts, the examined with great convenience, if a hole be made in
fifth or sixth will do ; because the globules of their the pedestal, to place the speculum exactly underneath,
blood are twice as large as those of frogs or fish. The and thereby throw up the rays of light. The pocket-
frst or second magnifier cannot well be employed for microscope, thus mounted, says Mr Baker, " is as easy
this purpose; because the thickness of the tube in and pleasant in its use ; as fit for the most curious ex-
which the object lies, will scarce admit its being amination of the animalcules and salts in fluids, of the
brought so near as the focal distance of the magni farinæ in vegetables, and of the circulation in small
fier.

animals ; in short, is as likely to make considerable
An apparatus for the purpose of viewing opaque discoveries in objects, that bave some degree of trans-
objects generally accompanies this microscope ; and parency, as any microscope I have ever seen or heard
which consists of the following parts. A brass arm
QR, which is screwed at Q, upon the body of the mi The brass scroll A is now generally made to un-
eroscope at G. Into the round hole R, any of the screw into three parts, and pack with the microscope
magnifiers suitable to the object to be viewed are to and apparatus into the drawer of a mahogany pocket.
be screwed; and under it, in the same ring, the con case, upon the lid of which the scroll is made to fix
cave polished silver speculum S. Through a small wben in use.
aperture in the body of the microscope under the The opaque apparatus also, as above described, is
brass plates EE, is to slide the long wire with the applicable this way by reflection. It only consists in
forceps T: This wire is pointed at one of its ends ; turping the arm Ř (fig. 1.), with the magnifier over
and so, that either the points or forceps may be used the concave speculum below (fig. 2.), or to receive
for the objects as may be necessary.

It is

the light as reflected obliquely from it: the silver speconceive, therefore, that the arm at R, which turns culum screwed into R will then reflect the light, which by a twofold joint at a and b, may be brought with it receives from the glass speculum, 'strongly upon the its magnifier over the object, the light reflected upon object that is applied upon the wire T underneath. it by the application of the speculum, and the true This miscroscope, however, is not upon the most focus obtained by turning of the male screw CC as convenient construction, in comparison with others now before directed.-As objects are sometimes not well made: it has been esteemed for many years past from fixed for view, either by the forceps or point, the its popular name, and recommendation by its makers. small piece shown at V is added, and in such cases Its portability is certainly a great advantage in its faanswers better : it serews over the point of T; it con vour ; but in most respects it is superseded by the mitains a small round piece of ivory, blackened on one croscopes hereafter described. side, and left white upon the other as a contrast to 3. Microscope for Opaque Objects, called the Single Fig. 3. coloured objects, and by a small piece of watch-spring Opaque Microscope. This microscope remedies the infastens down the objects upon the ivory.

convenience of having the dark side of an object next

of."

easy to

[ocr errors]

Micro the eye, which formerly was an insurmountable ob scope, screw the speculum, wità the magnifier you scope. jection to the making observations on opaque objects think proper to use, into the brass ring 1. Place your scope

with any considerable degree of exactness or satisfac object, either on the needle G in the pliers H, on the tion : for

, in all other contrivances commonly known, object-plate M, or in the hollow brass box o, as may the nearness of the instrument to the object (when be most convenient ; then holding up your instrument glasses that magnify much are used) unavoidably over by the handle P, look against the light through the shadows it so much, that its appearance is rendered ob- magnifying lens ; and by means of the nut D, together scure and indistinct. And, notwithstanding ways have with the motion of the neodle, by managing its lower been tried to point light upon an object, from the sun. end, the object may be turned about, raised, or deor a candle, by a convex glass placed on the side there pressed, brought nearer the glass, or removed farther of, the rays from either can be thrown upon it in such from it, till you find the true focal distance, and the an acute angle only, that they serve to give a confused light be seen strongly reflected from the speculum upglare, but are insufficient to afford a clear and perfect on the object, by which means it will be shown in a view of the object. But in this microscope, by means of manner surprisingly distinct and clear; and for this a concave speculum of silver highly polished, in whose purpose the light of the sky or of a candle will answer centre a magnifying lens w placed, such a strong and very well. Transparent objects may also be viewed by direct light is reflected upon the object, that it may be this microscope ; only observing, that when such come examined with all imaginable ease and pleasure. The under examination, it will not always be proper to several parts of this iostrument, made either of brass or throw on them the light reflected from the speculum ; silver, are as follow.

for the light transmitted through them, meeting the reThrough the first side A, passes a five screw B, the flected light, may together produce too great a glare. other end of which is fastened to the moveable side C. A little practice, however, will show how to regulate D is a nut applied to this screw, by the turning of both lights in a proper manner. which the two sides A and C are gradually brought 4. Ellis's single and Aquatic Microscope. Fig. 4. re- Fig. 4. together. E is a spring of steel that separates the presents a very convenient and useful microscope, contwo sides when the nut is unscrewed. F is a piece of trived by Mr John Ellis, author of An Essay upon Cobrass, turning round in a socket, whence proceeds a rallines, &c. To practical botanists, observers of anismall spring tube moving upon a rivet; through which malcula, &c. it possesses many advantages above those tube there runs a steel wire, one end whereof termi just described. It is portable, simple in its construcnates in a sharp point G, and the other with a pair of tion, expeditious, and commodious in use.

K repliers H fastened to it. The point and pliers are to presents the box containing the whole apparatus : it thrust into, or take up and hold, any insect or object; is generally made of fish-skin; and on the top there and either of them may be turned upwards, as best is a female screw, for receiving the screw that is at the suits the purpose. I is a ring of brass, with a female bottom of the pillar A: this is a pillar' of brass, and screw within it, mounted on an upright piece of the is screwed on the top of the box. D is a brass piu same metal ; whicb turos round on a rivet, that it may which fits into the pillar; on the top of this pin is a be set at a due distance when the least magnifiers are hollow socket to receive the arm which carries the employed. This ring receives the screws of all the magnifiers; the pin is to be moved up and down, in magnifiers. K is a concave speculum of silver, po order to adjust the lenses to their focal or proper dislished as bright as possible ; in the centre of which is tance from the object. [N. B. In the representaplaced a double convex lens, with a proper aperture tions of this microscope, the pin D is delineated as to look through it. On the back of this speculum a passing through a socket at one side of the pillar A; male screw L'is made to fit the brass ring I, to screw whereas it is usual at present to make it pass

down into it at pleasure. There are four of these concave hole bored through the middle of the pillar.] E, the specula of different depths, adapted to four glasses of bar which carries the magnifying lens; it fits into the different magnifying powers, to be used as the ob socket X, which is at the top of the pin or pillar D. jects to be examined may require. The greatest mag This arm may be moved backwards and forwards in nifiers have the least apertures. M is a round object the socket X, and sideways by the pin D; so that the plate, one side of which is white and the other black : magnifier, which is screwed into the ring at the end The intention of this is to render objects the more vi E of this bar, may be easily made to traverse over any sible, by placing then, if black, on the white side, part of the object that lies on the stage or plate B. or, if white, on the black side. A steel spring N turns FF is a polished silver speculom, with a magnifying down on each side to make any object fast; and is lens placed at the centre thereof, wbich is perforated suing from the object-plate is a hollow pipe to screw for this purpose. The silver speculum screws into the it on the needle's point G. O is a small box of brass, arm E, as at F. G, another speculum, with its lens, with a glass on each side, contrived to confine any li which is of a different magnifying power from the ving object, in order to examine it: this also has a former. H, the semicircle which supports the mirror I; pipe to screw upon the end of the needle G. Pis the pin R, affixed to the semicircle H, passes through turned handle of wood, to screw into the instrument the hole which is towards the bottom of the pillar A. when it is made use of. Q, a pair of brass pliers to B, the stage, or the plane, on which the objects are to take up any object, or manage it with conveniency. be placed; it fits into the small dove-tailed arm whick R is a soft hair-brush for cleaning the glasses, &c. Sis is at the upper end of the pillar DA. C, a plane a small ivory box for talcs, to be placed, when wanted, glass, with a small piece of black silk stuck on it; this in the small brass box 0.

glass is to lay in a groove made in the stage C. M, When you would siew any object with this micro a hollow glass to be laid occasionally on the stage in

stead

[ocr errors]

a

A 2

1

Micro- stead of the plane glass C. L, a pair of vippers, be fixed in the nippers MN, and then brought under the Micro. scope. These are fixed to the stage by the pin at bottom; eye-glasses; or they may be laid on one of the glasses scope.

the steel wire of these nippers slides backwards and which fit the stage. The apparatus to this instrument
forwards in the socket, and this socket is moveable consists of three ivory sliders; a pair of nippers ; a pair
upwards and downwards by means of the joint, so that of forceps ; a flat glass and a concave ditto, both fiited
the position of the object may be varied at pleasure. to the stage.
The object may be fixed in the nippers, stuck on the The two last microscopes are frequently fitted up
point, or affixed, hy a little gum-water, &c. to the with a toothed rack and pinion, for the more ready ad-
ivory eylinder N, which occasionally screws to the point justment of the glasses to their proper focus.
of the nippers.

6. Withering's portable Botanic Microscope. Fig. 6. Fig. 6.
To use this microscope : Take all the parts of the represents a small botanical microscope coptrived by
apparatus out of the box ; then begin by screwing the Dr Withering, and described by bim in his Botanical
pillar A to the cover thereof; pass the pin R of the Arrangements. It consists of three brass plates, ABC,
semicirele which carries the mirror through the hole wbich are parallel to each other; the wires D and E
that is near the bottom of the pillar A ; push the stage are rivetted into the upper and lower plates, which are
into the dove-tail at B, slide the pin into the pillar (see by this means united to each other; the middle plate
the N. B. above); then pass the bar E through the or stage is moveable on the aforesaid wires by two little
socket which is at the top of the pin D, and screw one

sockets which are fixed to it. The two upper plates
of the magnifying lenses into the ring at F. The mi- each contain a magnifying leds, but of different powers ;
croscope is now ready for use : and though the enume- one of these confines and keeps in their places the fine
ration of the articles may lead the reader to imagine the point F, the forceps G, and the small knife H.-T.
instrument to be of a complex nature, we can safely use this instrument, unscrew the upper lens, and take
affirm that he will find it otherwise. The instrument out the point, the knife, and the forceps ; then screw
has this peculiar advantage, that it is difficult to put the lens on again, place the object ou the stage, and
any of the pieces in a place which is appropriated to an- then move it up or down till you have gained a dis-
other. Let the object be now placed either on the tinct view of the object, as one lens is made of a shorter
stage or in the nippers L, and in such manner that it focus than the other; and spare lenses of a still deeper
may be as nearly as possible over the centre of the stage : focus may be bad if required. This little microscope
bring the speculum F over the part you mean to obe is the most portable of any. Its principal merit is its
serve ; then throw as much light on the speculum as simplicity.
you can, by means of the mirror ), and the double mo. 7. Botanical Lenses or Magnifiers. The haste with
tion of which it is capable ; the light received on the which botanists, &c. have frequently occasion to view
speculum is reflected by it on the object

. The distance objects, renders an exterpore pocket-glass indispen-
of the lens F from the object is regulated by moving sably necessary. The most convenient of any yet con-
the pin D up and down, until a distinct view of it is structed, appears to be that contrived, in regard to the
obtained. The best rule is, te place the lens beyond form of the mounting, by Mr Benjamin Martin; and
its focal distance from the object, and then gradually is what he called a Hand Megalascope, because it is
to slide it down till the object appears sharp and well well adapted for viewing all the larger sort of small
defined. The adjustment of the lenses to their focus, objects universally, and by only three lenses it has seven
and the distribution of the light on the object, are what different magnifying powers.
require the most attention : on the first the distinctness Fig. 7. represents tbe case with the three frames and Fig. 7.
of the vision depends ; the pleasure arising from a clear lenses, which are usually of 1, 1), and 2 inches focus :
view of the parts under observation is due to the modi, they all tum over each other, and shut into the case,
fication of the light. No precise rule can be given for and are turned out at pleasure. .
attaining accurately these points ; it is from practice The three lenses singly, afford three magnifying
alone that ready habits of obtaining these necessary pro- powers; and by combining two and two, we make three
perties can be acquired, and with the assistance of this more: for d with e makes one, d with f another, and
uo difficulty will be found.

e with f a third ; wbich, with the three singly, make
5. A very simple and convenient microscope for six; and lastly, all three combined together make an-
botanical and other purposes, though inferior in many other; so that upon the wbole, there are seven powers
respects to that of Mr Elis, was contrived by the of magnifying with these glasses only.
ingenious Mr Benjamin Martin, and is represented at When the three lenses are combined, it is better to
fig. 5. where AB represents a small arm supporting turn them in, and look through them by the small aper-
two or more magnifiers, ope fixed to the upper part tures in the sides of the case. The eye in this case
as at R, the other to the lower part of the arm at C; is excluded from extra light; the aberration of the
these may be used separately or combined together. Superfluous rays through the glasses is cut off; and the
The arm AB is supported by the square pillar IK, eye coincides more exactly with the common axes of
the lower end of which fits into the socket E of the the lenses.
foot FG; the stage DL is made to slide up and down A very useful and easy kind of microscope (deserib- Plate

cccxxxvii.
the square pillar; H, a concave mirror for reflecting ed by Joblot, and which has been long in use), adapt-
light on the object. To use this microscope, place the ed chiefly

, for viewing, and confining at the same time,
object on the stage, reflect the light on it from the any living inseets, small animals, &c. is shown at fig. 8. Fig. 8.
concave missor, and regulate it to the facus, by moving wbere A represents a glass tube, about 13 inch dia-
the stage nearer to or fartber from the lens at B. The meter, and 2 inches high. B, a case of brass or wood,
sory sliders pass through the stage ; other objects may containing a sliding tube, with two or three magnify-

Fig 5.

Fig. 9

Micro- ing glasses that may be used either separately or com The particular and chief advantages which the corh- Micró. scope. bined. In the inside, at the bottom, is a picce of ivory, pound microscopes have over the single, are, that the scope. be black and white on opposite sides, that is occasionally objects are represented under a larger field of view, and

removed, and admits a point to be screwed into the with a greater amplification of reflected light.
centre. The cap unscrews at D, to admit the placing 1. Culpeper's MicroscoppoThe compound microscope,
of the object : the proper distance of the glasses from originally contrived by Mr Culpeper, is represented at
the object is regulated by pulling up or down the brass fig. 10. It consists of a large external brass body A, Fig. 10.
tube É at top containing the eye-glasses.

B, C, D, supported upon three serolls, which are fixed This microscope is particularly useful for exbibiting to the stage EF; the stage is supported by three larthe well-known curicus curculio imperialis, vulgarlyger scrolls, that are screwed to the mabogady pedestal called the diamond beetle, to the greatest advantage ; GH. There is a drawer in the pedestal, which holds for which, as well as for other objects, a glass bottom, the apparatus. The concave mirror I is fitted to a and a polished reflector at the top, are often applied, socket in the centre of the pedestal. The lower part to condense the light upon the object. In this case, LMCD of the body forms an exterior tube, into which the stand and brass-bottom F, as shown in the figure, the upper part of the body ABLM slides, and may are taken away by unscrewing.

be moved up or down, so as to bring the magnifiers, 9.

Mr Lyonet's Single Anatomical Dissecting Micro- which are screwed on at N, nearer to or farther from scope.-Fig. 9. represents a curious and extremely use

the object.
ful microscope, invented by that gentleman for the pur To use this microscope : Screw one of the buttons,
pose of minute dissections, and microscopic prepara- which contains a magnifying lens, to the end N of the
tions. This instrument must be truly useful to ama body: place the slider, with the objects, between the
teurs of the minutiæ of insects, &c. being the best plates of the slider-holder. Then, to attain distinct
adapted of any for the purposes of dissection. With vision, and a pleasing view of the object, adjust the
this instrument Mr Lyonet made his very curious mi. body to the focus of the lens you are using, by moving
croscopical dissection of the chenille de saule, as related the upper part gently up and down, and regulate the
in his Traité Anatomique de la chenille qui ronge le bois light by the concave mirror.
de saule, 4to.

For opaque objects, two additional picces' must be
AB is the anatomical table, which is supported

by used. The first is a cylindrical tube of brass (represent-
a pillar NO; this is screwed on the foot CD). The ed at L, fig. 11.), which fits on the cylindrical part at Fig. 1r.
table AB is prevented from turning round by means N of the body. The second piece is the conca ve speolx
of two steady pins. In this table or board there is a lum h; this is to be screwed to the lower end of the
hole G, which is exactly over the centre of the mirror aforesaid tube: the upper edge of this tube should be
EF, that is to reflect the light on the object; the hole made to coincide with the line which has the same nama
G is designed to receive a flat or concave glass, on ber affixed to it as to the magnifier you are using ; e.g.
which the objects for examination are to be placed. if you are making use of the magnifier marked S, slide

RXZ is an arm formed of several balls and sockets, the tube to the circular line on the tube N that is by which means it may be moved in every possible si marked also with No 5 The slider-bolder slwuld be tuation; it is fixed to the board by means of the screw removed when you are going to view opaque oba H. The last arm IZ has a female serew, into which jects, and a plane glass sbould be placed on the stage a magnifier may be screwed as at Z. By means of the in its stead to receive the object; or it may be placed screw H, a small motion may be occasionally given to in the nippers, the pin of which fits into the hole in the the arm ÍZ, for adjusting the lens with accuracy to its stage. focal distance from the object.

The apparatus belonging to this microscope consists Another chain of balls is sometimes used, carrying a of the following particulars: viz. Five magnifiers, eachi lens to throw light upon the object ; the mirror is like fitted in a brass button ; one of these is seen at N, wise so mounted, as to be taken from its place at K, and fig. 10. Six ivory, sliders, five of them with objects. fitted on a clamp, by which it may be fixed to any part A brass tube to hold the concave speculum, The of the table AB.

concave speculum in a brass box. A fish pan. A set To use the Dissecting Table.-Let the operator sit of glass tubes. A flat glass fitted to the stage. A with his left side near a light window; the instrument concave glass fitted to the stage. A pair of forceps. being placed on a firm table, the side DH towards the

A. steel wire, with a pair of nippers at one end and a stomach, the observations should be made with the point at the other. A small ivory cylinder, to fit'on left eye. In dissecting, the two elbows are to be sup the pointed end of the aforesaid nippers. A convex ported by the table on which the instrument rests, the lens, movcable in a brass semicircle ; this is affixed to hands resting against the board, AB; and in order to a long brass pin, which fits into a hole on the stage. give it greater stability, (as a small shake,, though im The construction of the foregoing microscope is very perceptible to the naked eye, is very visible in the mi- simple, and it is easy in use; but the advantages of the croscope), the dissecting instruments are to be held stage and mirror are too much confined for an extensite one in each band, between the thumb. and two fore- ' application and management of all kinds of objects. Its fingers.

greatest recommendation is its cheapness ;; and to those

who are desirous of having a compound microscope at II. Of DOUBLE Mieroscopes, commonly called Com

a low price, it may be acceptable. POUND Alteroscopes.

2. Cuff's Microscope.--The improved microscope Double microscopes are so called, from being a com next in order is that of Mr Cuff. Besides remedying tination; of two or more lenses.

the disadvantages above mentioned, it contains thos

addition

scope.

screw c

Niicro- addition of an adjusting screw, which is a consider- ivory box, to hold a supply of talc and rings for the Mi-To.

able improvement, and liighly necessary to the ex sliders. V, a small ivory cylinder, that fits on the scope.

amination of objects under the best defined appear- pointed end of the steel wire : it is designed for opaque Fig. 11. ance from the glasses. It is represented at fig. 11. objects. Light-coloured ones are to be stuck upon

with the apparatus that usually accompanies it. A, the dark side, and vice versa. M, a fish-pan, whereon
B, C, shows the body of this microscope ; which to fasten a small fish, to view the circulation of the
contains an eye-glass at A, a broad lens at B, and blood : the tail is to be spread across the oblong hole
a magnifier which is screwed on at C. The body k at the small end, and tied fast, by means of a rib-
is supported by the arm DE, from which it may band fixed thereto; the knob l is to be shoved through
be removed at pleasure. The arm DE is fixed the slit made in the stage, that the tail may be brought
on the sliding bar F, and may be raised or depres- under the magnifier.
sed to any height within its limits.

The main pil 3. This microscope has received several material imlar a b is fixed in the box be; and by means of the provements from Mr Martin, Mr Adams, &c. By brass foot d is screwed to the mahogany pedestal XY, an alteration, or rather an enlargement, of the body of in which is a drawer containing all the apparatus. Oʻis the tube which contains the eye-glasses, and also of the a milled-headed screw, to tighten the bar F when the eye-glasses themselves, the field of view is made much adjusting screw eg is used. p q Is the stage, or plate, larger, the mirror below for reflecting light is made to which carries the objects; it has a hole at the centre move upon the same bar with the stage ; by which means n. G, a concave mirror, that may be turned in any the distance of it from the stage may be very easily and direction, to reflect the light of a candle, or the sky, suitably varied. A condensing glass is applied under upon the object.

the stage in the slider-holder, in order to modify and To use this microscope : Screw the magnifier you increase the light that is reflected by the mirrors beintend to use to the end of the body; place the low from the light of a candle or lamp. It is furnishslider-bolder P in the hole n, and the slider with the ed also with two mirrors in one frame, one concave object between the plates of the slider-holder; set the and the other plane, of glass silvered ; and by simply upper edge of the bar DE to coincide with the di unscrewing the body, the instrument, when desired, may visions which correspond to the magnifier you have in be converted into a single microscope. Fig. 12. is a Fig. 120. * use, and pinch it by the milled nut ; now reflect a representation of the instrument thus improved; and proper quantity of light upon the object, by means of the following is the description of it, as given by the concave mirror G, and regulate the body exactly Mr Adams in his Essays. to the eye and the focus of the glasses by the adjusting AB represents the body of the microscope, conc8

taining a double eye-glass and a body-glass; it is To view opaque objects, take away the slider-holder here shown as screwed to the arm CD, from whence P, and place the object on a flat glass under the cen it may be occasionally remo

moved, either for the convetre of the body, or on one end of the jointed pippers nience of packing, or when the instrument is to be used op. Then screw the silver concave speculum h to the as a single microscope. end of the cylinder L, and slide this cylinder on the The eye-glasses and the body-glasses are contained lower part of the body, so that the upper edge thereof in a tube which fits into the exterior tube AB ; by may coincide with the line which has the same mark pulling out a little this tube when the microscope is in with the magnifier that is then used : reflect the light use, the magnifying power of each lens is increased. from the concave mirror G to the silver speculum, The body AB of the microscope is supported by from which it will again be reflected on the object. the arm CD; this arm is fixed to the main pillar CF, The glasses are to be adjusted to their focal distance as which is screwed firmly to the mahogany pedestal before directed.

GH; there is a drawer to this pedestal, which holds The apparatus consists of a convex lens H, to col the apparatus, lect the rays of light from the sun or a candle, and NIS, the plate or stage which carries the slider-bolder condense them on the object. La cylindrical tube, KL; this stage is moved up or down the pillar CF, by open at each side, with a concave speculum screwed to turning the milled nut M; this nut is fixed to a pinion, the lower end h. P the slider-bolder: this consists of a that works in a toothed rack cut on one side of the pil. cylindrical tube, in which an inner tube is forced up- lar. By means of this pinion, the stage may be graduwards by a spiral spring; it is used to receive an ivory ally raised or depressed, and the object adjusted to the slider K, which is to be slid between the plates h focus of the different lenses. and i. The cylinder P fits the hole n in the stage ; KL is a slider-holder, which fits into a hole that is in and the hollow part at k is designed to receive a glass the middle of the stage NIS; it is used to confine and tube. R is a brass cone, to be put under the bottom guide either the motion of the sliders which contain the of the cylinder P, to intercept occasionally some of objects, or the glass tubes that are designed to confine the

rays of light. S, a box containing a concave and small fishes for viewing the circulation of the blood. a flat glass, between which a small living insect may The sliders are to be passed between the two upper be confined: it is to be placed over the hole n. T, plates, the tubes through the bent plates. a flat glass, to lay any occasional object upon ; there L is a brass tube, to the upper part of which is fixed is also a concave one for fluids. O is a long steel wire, the condensing lens before spoken of; it fits into the with a small pair of pliers at one end, and a point at under part of the slider-holder KL, and may be set at the other, designed to stick or hold objects : it slips different distances from the object, according to its disbackwards and forwards in the short tube o; the pin tance from the mirror or the candle. p fits into the hole of the stage. W, a little round O is the frame wbich holds the two reflecting mir

rors,

« AnteriorContinuar »