Part 11

A B C D, Fig. 4, represents the body of the microscope, consisting of two brass tubes. E F is the end of the inner moveable tube; _e f_, that of the single tooth and pinion microscope. Fig. 5, screws into the end of this inner tube; at the end, A B, of the external tube there is a convex lens, to receive the sun’s rays from the mirror, K L, and to condense them on the object; the end, A B, screws into the circular plate, G H I. This part may also be used as a single microscope, and may have at _m_ the handle, _c_, screwed to it. K L, a long frame fixed to the moveable circular plate, with a plane mirror, to reflect the rays of the sun on the lens at A B. An endless worm or screw, which is cut on the lower part of the nut, M, works in a small wheel which is fixed to the frame, K L, so that by turning the nut, the frame, K L, is moved up or down: the nut, N, moves the mirror to the right or left. O, P, two screws to fasten the square plate to the window-shutter.

Fig. 5, the single microscope; _e f_, the end which screws on to the part, E F, Fig. 4, of the internal tube of the body; _q_, the dove-tailed slit for receiving the slider, Fig. 8; _g_, the hole in which the megalascope magnifier, Fig. 6, is to be screwed, when the slider, Fig. 8, is removed. At _h_, are the moveable plates, between which the object sliders are placed; under the lowermost of these, the lens represented at Fig. 11 is to be placed, when the magnifiers in the slider, Fig. 8, are to be used, _a k_ is a small piece of rack-work, which is moved backwards and forwards by the pinion fixed to the milled nut, _b_; by the gradual motion of this rack, the objects are adjusted to the foci of the different lenses. Fig. 8 is a brass slider, with six lenses, or magnifying glasses; it is to be inserted into the hole at _q_; either of the magnifiers may be placed before the object, by sliding it one way or the other: you may perceive when the glass is in the center of the eye-hole by a small spring acting upon a notch which is made on the side of the slider opposite to each lens.

APPARATUS BELONGING TO THIS SOLAR MICROSCOPE.

Square plate and mirror. The body, A D, consisting of two tubes, one within the other. The single microscope, Fig. 5. The megalascope lens, Fig. 6. The slider, Fig. 8, with six lenses. The two screws O, P. Six ivory sliders and a talc box, Fig. 7 and 13. Some glass tubes, Fig. 9. A slider or brass case, Fig. 10, containing a plane piece of glass, and a brass slider with holes, into which are cemented small concave glasses, designed for confining minute insects between the plane and concave glasses, which are thus preserved from being crushed, or from moving out of the field of view. Three condensing lenses to enlarge the field of view, such as Fig. 11, that are fitted to the hole, _l_, of Fig. 5. Their numbers correspond with the numbers used. Fig. 12, two brass nuts for the window-shutter or board, to receive the two screws, O and P.

TO USE THE TRANSPARENT SOLAR MICROSCOPE. Fasten the square plate against the inside of a window-shutter, by the two screws O, P, which are to go from the outside of the window-shutter through it, and then be screwed into their respective holes in the square plate at G H I. The mirror is to be on the outside of the shutter, passing through a hole made for that purpose. Darken the room; then place a screen at about six or eight feet distance from the window, the farther it is from it the larger is the image: now move the mirror, K L, by the two nuts M N, till the sun’s rays come through the instrument in an horizontal direction to the screen, forming a round spot thereon; screw the microscope, Fig. 5, into its place E F; put the slider with the lenses, Fig. 8, at _q_, Fig. 5, and the object slider between the plates at _h_; adjust the object to the focus of the magnifying lens by the screw _b_, till the object appears distinct and clear on the screen. By moving the internal tube of the body, the object may be placed at different distances from the lens which is fixed at A B, so as to be sufficiently illuminated, and not burnt by the solar rays. If the screws O, P, are to pass inside the room, the two nuts, Fig. 12, must be previously fixed.

THE SCREW BARREL, OR WILSON’S SINGLE POCKET MICROSCOPE. Plate II. B. Fig. 1 and 2.

This microscope of Mr. Wilson’s is an invention of many years standing, and was in some measure laid aside, till Dr. Lieberkühn introduced the solar apparatus to which he applied it, there being no other instrument at that time which would answer his purpose so well; it is much esteemed in particular cases. The body of the microscope is represented at A B, Fig. 1, and is made either of silver, brass, or ivory. C C is a long fine-threaded male screw, that turns into the body of the microscope. D, a convex glass at the end of the said screw, on which may be placed, as occasion requires, one of the two concave apertures of thin brass to cover the said glass, and thereby diminish the aperture when the greatest magnifiers are used. E, three thin plates of brass within the body of the microscope, one whereof is bent to an arched cavity for the reception of a tube of glass. F, a piece of wood or brass, curved in the manner of the said plate, and fastened thereto. G, the other end of the microscope, where a female screw is adapted to receive the different magnifiers. H, a spiral spring of steel, between the said end, G, and the plates of brass, E, intended to keep the plates in a due position, and counteract against the long screw, C. I, a small ivory handle. To this microscope belong seven different magnifying glasses, six of which are set in cells, as in Fig. K, and are marked from 1, to 6: the lowest numbers to the greatest magnifiers. L is the seventh magnifier, set in the manner of a little barrel, to be held in the hand for viewing any large object. M is an ivory slider with the objects. Six of these, and one of brass, are usually sold with this microscope. There is also a brass slider not shewn in the figure, to confine any small object, that it may be viewed without crashing or destroying it. N, a pair of forceps, or pliers, for the taking up of insects or other objects, and applying them to the sliders or glasses. O, a camel hair brush, to take up and examine a small drop of liquid, brush the dust away, &c. P is a glass tube to confine living objects, such as frogs, fishes, &c.

When you view an object, push the ivory slider, in which the said object is placed, between the two flat brass plates, observing always to put that side of the slider, where the brass rings are, farthest from the eye; then screw in the magnifying glass you intend to use at the end of the instrument G, and looking through it against the light, turn the long screw, C C, till your object is brought to appear distinct, or to the true focal distance. To examine any object accurately, view it first through a magnifier that will shew the whole at once, and afterwards inspect the several parts more particularly with one of the greatest magnifiers; for thus you will gain a true idea of the whole, and all its parts: and, though the greatest magnifiers can shew but a minute portion of any object at once, such as the claw of a flea, the horn of a louse, &c. yet by gently moving the slider that contains your object, the eye will gradually see the whole; and if any part should be out of the focal distance, the screw, C C, will easily bring it to the true focus. As objects must be brought very near the glass, when the greatest magnifiers are used, be particularly careful not to rub the slider against the glasses as you move it in or out. A few turns of the screw, C C, will easily obviate this.

DESCRIPTION OF A SCROLL FOR FIXING WILSON’S POCKET MICROSCOPE, AND A MIRROR FOR REFLECTING LIGHT INTO IT.

A B C, Fig. 2, is a brass scroll, which, for the better conveniency of carriage, is made to unscrew into three parts, and may be put into the drawer upon which it stands, with its reflecting mirror D, and Wilson’s pocket microscope, G. The upper part of the scroll is taken off at B, by unscrewing half a turn of the screw; then, if lifted up, it will come out of the socket. The lower part unscrews at C, and the base at E. The mirror lifts out at F, which, with the scroll, lies in one partition of the box.

To apply this scroll for use, fix the body of the microscope to the top thereof by the screw, A, as in Fig. 2, by screwing it in the same hole as the ivory handle was applied to before. The brass or ivory slider being fixed as before described, and the microscope placed in a perpendicular position, move the mirror, D, in such a manner as to reflect the light of the sky, of the sun, or a candle, directly upwards through the microscope; by which means the object will be most conveniently viewed. It is further useful for viewing opake objects, by screwing the arm, Q R, Fig. 1, into the body of the microscope at G; then screwing into the round hole, R, that magnifier which you think will best suit your object, and putting the concave speculum, S, on the outside of the ring, R, you will observe in the body of the microscope, between the wood or brass, F, and the end of the male screw, C C, a small hole, _u_, through which slides the long wire, T, which has a point at one end, and forceps at the other, that may be used occasionally as your objects require. When you have fixed this, and your object on it, turn the arm, R, till the magnifier is brought over the object; it may be then adjusted to the true focus, by turning the screw, as before. It must also be brought exactly over the speculum, by turning the upper part of the scroll to one side, till your object and the two specula are in one line, as will be found by trial; and then fix it by the screw, B, at which time the upper surface of the object will be enlightened by the light reflected from the mirror, D, to the concave speculum.

DESCRIPTION OF A SMALL MICROSCOPE FOR OPAKE OBJECTS. Plate II. B. Fig. 3 and 4.

A, Fig. 3, is a fixed arm, through which passes a screw, B, the other end is fastened to the moveable arm, C. D, a nut fitted to the said screw, which, when turned, will either separate or bring together the two arms, A C. E, a steel spring, that separates the two sides when the nut is unscrewed. F, a piece of brass turning round in a spring socket, moving on a rivet, in which moves a steel wire pointed at the end G, and the other end a pair of pliers, H: these are either to thrust into, or take up and hold any object, and may be turned round as required. I, a ring of brass, with a female screw fixed on an upright piece of the same metal, turning on a rivet, that it may be set at a due distance when the least magnifiers are used, and is adapted to the screws of all the magnifiers.

Fig. 4, K, a concave speculum of polished silver, in the center of which a lens is placed. On the back of this speculum a male screw, L, is made to fit the brass ring I, Fig. 3. Four of these specula of different concavities, with four glasses of different magnifying powers, as the objects may require. The greatest magnifiers have the least apertures. M, a round object plate, one side white and the other black, intended to render objects the more visible, by placing them, if black, upon the white, and if white, on the black side. A steel spring, N, turns down on each side, to secure any object; from the object plate there is a hollow pipe, to screw it on the needle’s point G, Fig. 3. O, a small box of brass, with a glass on each side, to confine any living object in order to examine it, having a pipe to screw upon the end of the needle at G. P, an ivory handle. Q, a pair of pliers to take up any object. R, a soft hair brush.

To view any object, screw the speculum, with the magnifier you intend to use, into the brass ring, I; place your object either on the needle G, in the pliers H, on the object plate M, or in the brass hollow box O, as may be most convenient; then holding up your instrument by the handle P, look against the light through the magnifying lens, and by means of the nut, D, together with moving of the needle at its lower end, the object may be turned about, raised or depressed, brought nearer the glass, or put farther from it, till you have the true focal distance, and the light be seen reflected from the speculum strongly upon the object.[35]

[35] Opake microscopes are now constructed more elegantly and simply. The chief merit of Wilson’s microscope appears, in being particularly adapted to minute objects, and these principally of the transparent kind; the barrel form is useful for excluding adventitious light. Excepting these peculiarities, its general utility is considered far short of the universal pocket microscope hereafter to be described. EDIT.

OF ELLIS’S SINGLE OR AQUATIC MICROSCOPE. Plate VII. B.

This instrument takes its name from Mr. John Ellis, author of “An Essay towards a Natural History of Corallines,” and of the “Natural History of many curious and uncommon Zoophytes.” By this instrument he was enabled to explain many singularities in the œconomy and construction of these wonderful productions of nature. To the practical botanist this instrument is recommended by the respectable authority of Mr. Curtis, author of the Flora Londinensis, a work which does credit to the author and the nation. This microscope is simple in its construction, easy in its use, and very portable; these advantages, as well as some others which it also has over other portable microscopes, have accelerated the sale thereof, and caused it to be very much adopted.

DESCRIPTION OF THE VARIOUS PARTS OF THE MICROSCOPE.

K, the box which contains the whole apparatus; it is generally made of fish-skin; on the top of the box there is a female screw, for receiving the screw which is at the bottom of the brass pillar A, and which is to be screwed on the top of the box, K. D, a brass pin which fits into the pillar; on the top of this pin is a hollow socket to receive the arm which carries the magnifiers; the pin is to be moved up and down, in order to adjust the lenses to their focal or proper distance from the object.

In the representation of this microscope, Plate VII. B. Fig. 1, the pin, D, is delineated as passing through a socket at one side of the pillar, A; it is now usual to make it pass down a hole bored through the middle of the pillar.

E, the bar which carries the magnifying lens; it fits into the socket, X, which is at the top of the pillar, D. This arm may be moved backwards and forwards in the socket X, and sidewise by the pin, D; so that the magnifier, which is screwed into the ring at the end, E, of this bar, may be easily made to traverse over any part of the object lying on the stage or plate B. F is a polished silver speculum, with a magnifying lens placed at the center thereof, which is perforated for this purpose. The silver speculum screws into the arm E, as at F. G, another speculum of a different concavity from the former, with its lens. H, the brass semicircle which supports the mirror, I; the pin, R, affixed to the semicircle, H, passes through the hole which is towards the bottom of the pillar, A. B, the stage or the plane on which the objects are to be placed; it fits into a small dove-tailed arm which is at the upper end of the pillar, A. C, a plane glass, with a small piece of black silk stuck on it; this glass is fitted to a groove made in the stage, B. M, a deep concave glass, to be laid occasionally on the stage instead of the plane glass, C. L, a pair of nippers; these are fixed to the hole of the stage, _a_, by the pin K; the steel wire of these nippers slides backwards and forwards in the socket, and this socket is moveable upwards and downwards by means of the joint, so that the position of the object may be varied at pleasure. The object may be fixed in the nippers, stuck on the point, or affixed by a little gum-water, &c. to the ivory cylinder, N. O, a small pair of brass forceps to take up minute objects by. P, a brush to clean the glasses.

To use this microscope; begin by screwing the pillar, A, to the cover thereof; pass the pin, R, of the semicircle which carries the mirror through the hole that is near the bottom of the pillar, A; push the stage into the dove-tail at B; slide the pin into the pillar, then pass the bar, E, through the socket, X, which is at the top of the pin D, and screw one of the magnifying lenses into the ring at F.

Now place the object either on the stage, or in the nippers L, and in such a manner, that it may be as nearly as possible over the center of the stage; bring the speculum, F, over the part you mean to observe; then get as much light on the speculum as you can, by means of the mirror, I; the light received on the speculum is reflected by it on the object. The distance of the lens, F, from the object is regulated by moving the pin, D, up and down, until a distinct view of it is obtained. The rule usually observed is, to place the lens beyond its focal distance from the object, and then gradually slide it down, till the object appears sharp and well defined. The adjustment of the lenses to their foci, and the distribution of the light on the object, are what require the most attention.

These microscopes are sometimes fitted up with a rack and pinion to the pillar A, and pin D, for the more ready adjustment of the glasses to their proper foci.

DESCRIPTION OF LYONET’S ANATOMICAL MICROSCOPE. Plate VI. Fig. 3.

Fig. 3 represents the instrument with which M. Lyonet made his microscopical and wonderful dissection of the chenille de saule or caterpillar of the goat moth,[36] of which a specimen is given in Plate XII. Fig. 1, &c. of this work. This portable instrument needs no further recommendation. By it, other observers may be enabled to dissect insects in general with the same accuracy as M. Lyonet, and thus advance the knowledge of comparative anatomy, by which alone the characteristic, nature, and rank of animals, can be truly ascertained.

[36] Phalæna cossus. Linn. 63.

A B is the anatomical table, which is supported by the pillar O N; this is screwed on the mahogany foot, D C. The table A B, is prevented from turning round by means of two steady pins; in this table or board there is a hole, G, which is exactly over the center of the mirror, F E, that is to reflect the light on the object; the hole, G, is, designed to receive a flat or a concave glass, on which the objects are to be placed that you design to examine or dissect. R X Z is an arm formed of several balls and sockets, by which means it may be moved in every possible position; it is fixed to the board by means of the screw, H; the last arm, I Z, has a female screw, into which a magnifier may be screwed, as at Z. By means of the screw, H, a small motion may be occasionally given to the arm I Z, for adjusting the lens with accuracy to its focal distance from the object. Another chain of balls is sometimes used, carrying a lens to throw light upon the object; the mirror is also so mounted, as to be taken from its place at K, and fitted on a clamp, by which it may be fixed to any part of the table, A B.

TO USE THE DISSECTING TABLE. Let the operator sit with his left side near a light window; the instrument being placed on a firm table, the side, D L, towards his breast, the observations should be made with the left eye: this position is well adapted for observing, drawing, or writing. In dissecting, the two elbows are to be supported by the table on which the instrument rests, the hands resting against the board, A B, in order to give it greater stability, as a small shake, though imperceptible to the naked eye, is very visible in the microscope; the dissecting instruments are to be held one in each hand, between the thumb and two fore-fingers. Farther directions are given on the mode of dissecting small objects in the following chapter.

DR. WITHERING’S BOTANICAL MICROSCOPE. Plate VI. Fig. 1.

This small instrument consists of three brass parallel plates, A, B, C; two wires, D and E, are rivetted into the upper and lower plate; the middle plate or stage is moveable on the aforesaid wires, by two little sockets which are fixed to it. The two upper plates each contain a magnifying lens, but of different powers; one of these confines and keeps in their places the fine point F, the forceps G, and the small knife H.

To use this instrument, unscrew the upper lens, and take out the point, the knife, and the forceps; then screw the lens on again, place the object on the stage, and then move it up or down till you have gained a distinct view of the object, as one lens is made of a shorter focus than the other; and spare lenses of a still deeper focus are sometimes added. The principal merit of this microscope is its simplicity.

THE POCKET BOTANICAL AND UNIVERSAL MICROSCOPE.

This pocket instrument is represented at Plate VI. Fig. 2. It is by most naturalists deemed preferable to Dr. Withering’s, being equally simple, more extensive in its application, and the stage unincumbered; though that of M. Lyonet seems better adapted than either to the purposes of dissection only.

A B, a small arm, carrying three magnifiers, two fixed to the upper part, as at B, the other to the lower part of the arm, at C; these may be used separately or combined together, by which you have seven powers. The arm, A B, is supported by the square pillar I K, the lower end of which fits into the socket, E, of the foot, F G; the stage, D L, is made to slide up and down the square pillar. H, a mirror for reflecting light on the object.

To use this microscope, place the object on the stage, L, reflect the light on it from the mirror H, and regulate it to the focus, by moving the stage nearer to or further from the lenses at B C. The ivory sliders pass under the stage, L; other objects may be fixed in the nippers, M N, and then brought under the magnifiers; or they may be laid on one of the glasses fitted to the stage. The apparatus to this instrument consists of three ivory sliders, a pair of nippers, a pair of forceps, a flat glass, and a concave ditto, all fitted to the stage, L. By taking out the pin, M, the pillar, I K, may be turned half round, and the foot, F G, made to answer as an handle.[37]

[37] An adjusting screw, Fig. 13*, to move the stage, with other additions, are made by Messrs. Jones; and which then, in my opinion, constitute the most complete pocket microscope hitherto made; for the particulars of which, I refer the reader to their printed description. Fig. 14, represents the common flower or insect microscope. There are two lenses, _a_ and _b_, that are used separately or conjointly. EDIT.

BOTANICAL MAGNIFIERS.

Since botany has been cultivated with so much ardor, it has been found necessary to contrive some very portable instrument, by which the botanist might investigate the object of his pursuits as it rises before him. Plate VIII. Fig. 7 and 8, represent two of the most convenient sort.

In the tortoiseshell case, Fig. 7, three lenses are contained, _d_, _e_, _f_, of different foci, which are all made to turn into the case, and may be used combined or separately. The three lenses in themselves afford three different magnifying powers; by combining two and two, we make three more; and the three together make, a seventh magnifying power. When the three lenses are used together, it is best to turn them into the case, and look through the hole, for more distinctness, and the exclusion of superfluous light. In the case, Fig. 8, are also three lenses, _g_, _h_, _i_, of different magnifying powers, that all turn up, and shut into the case; but these are not capable of combination.

DESCRIPTION OF A PORTABLE MICROSCOPE AND TELESCOPE. Plate VIII. Fig. 1, to 6.