Part 10

At the stage N I S, is a sliding brass spring, N, serving to confine down slips of glass or large sliders, when objects placed thereon are intended to be viewed out of the horizontal position of the stage. A lens, U, called the condensing lens, fixed in a frame connected to a socket, is for condensing and modifying the rays of light reflected from the concave or plane mirror, O, below; it may be set to a proper distance by raising it up by two little screws, one of which is shewn at _u_. This lens is of considerable use by candle-light, as it serves to fill the whole body, A B, beautifully with light on the object. It is turned aside on a joint pin, when not in use. Six magnifiers are contained in the wheel at P, as in the former microscope. The mirrors, O, below may also be slid upwards or downwards on the stem, by pushing against the screws at _r_. Thus the stage, lens U, and mirrors below, being all in one axis of motion, admit the adjustment of the distinct view, light, &c. in the most accurate and pleasing manner. When the instrument is packed into its case, the feet, G G H, may all be folded together as one, and the body A B, screwed off, for the advantage of being portable. The body, as screwed off, leaves the instrument a single microscope.

THE GENERAL APPARATUS TO THIS MICROSCOPE IS AS FOLLOWS.

First, such as accompany the preceding microscope. The brass wheel with magnifiers, P, Fig. 2. The slider-holder, K. The brass pin and arm, _a_, for receiving the concave speculum, _e_, which is applied to the upper side of the stage, and used common to all the magnifiers. The silver concave speculum, _f_, with a magnifier set therein, used by itself in the arm C D. These two speculums form the instrument into what is called an OPAKE MICROSCOPE.

A brass cone, g, fitting the under side of the stage, N I S, to exclude superfluous light. The illuminator, or convex lens, _d_, Fig. 1, fitted to T of the stage. The jointed nippers, _b_, fitted to the stage, and either on the point or nippers to hold any small insect, or other opake object. An ivory black and white piece, _h_, is also fitted to the point to contrast the colour of any object laid thereon; the light upon this is reflected from the silver concaves placed above, which reflect the light downwards received from the mirrors at O. Six ivory sliders as shewn at _i_, containing a selection of objects, placed between Muscovy talc, and fastened by spring wires; and a brass frame slider, _k_: all for the stage, K, when in use. A set of glass tubes for fish or liquids, _l_, to be filled with water and stopped with cork, for the slider-holder K. A pan, _c_, for fish or frogs, fitted to the stage at S. A small ivory box, _m_, with spare talcs and wires. The explorator, _n_, a lens set in a brass cell, for viewing the larger sort of objects either by the hand, or from the arm C D, Fig. 2. A plane glass, _o_, and a concave ditto, _s_, both fitted to the hole of the stage, N I S, for viewing fluids, and confining the animalcula, &c. between them, and so forming what is called the AQUATIC MICROSCOPE.

A brass box, _p_, with a concave and plane glass, for insects and other objects, fitted to the stage N I S, when they are to be examined by the instrument. A pair of brass forceps, _q_, to take or hold any object by. A camel hair brush, _t_.

ADDITIONAL APPARATUS TO THIS BEST MICROSCOPE.

Three large wood sliders, as shewn at X, with talcs and wires, for the larger sort of wings of flies, and other objects which are too large for the small ivory sliders, _i_; they are to be placed in the slider-holder K, when on the stage N I S, and the objects to be magnified either by the magnifiers in the wheel P, or the lens shewn at _n_, screwed on the arm C D. A brass cell, _y_, with a very small globule or lens, or an extraordinary great magnifier, usually about the 30th or 40th of an inch focus; it is to be screwed into the arm C D, when the wheel, P, is first unscrewed away. It is for the purpose of viewing extreme minute objects, which may be so small as to elude the power of the magnifiers in the wheel, P.

A moveable stage, W, which by the pin, _a_, is applied to the hole, S, of the stage Fig. 2, and thereby has an horizontal motion under the whole field of view, without disturbing any other part of the instrument. To the large hole of this stage are fitted a deep concave glass, _r_, and the concave and plane glasses, _s_ and _o_; and to the small holes, _x_ _x_, a black and white piece of ivory, _w_, for opake objects, and a concave and plane glass similar to _o_ and _s_. An extra concave silver speculum with a less magnifier than the other, as shewn at _f_, used for the larger kind of opake objects, like the other, fitted to the arm C D, and used instead of the magnifiers in the wheel, P.

Rack-work is sometimes cut in the arm C D, to turn the pinion above, so as to move the magnifiers in a linear direction over the objects in the most accurate degree; and also the stage N I S jointed, to turn by a screw and teeth in an horizontal direction at right angles to the above, thereby rendering a slow and accurate motion, perfectly suitable to the various positions of any living animal under examination.

Six or more larger ivory sliders, with cuttings of different woods, &c. are also frequently added; but as these enhance the expense, and may be extended to the desire of the purchaser, his choice, and not my description here, will determine the extent of the apparatus to the microscope. When packed up into its mahogany, or black shagreen case, the outside dimensions are about twelve inches and an half long, nine inches broad, and three inches three-quarters deep.

A microscope from this plan is frequently made of smaller dimensions, for the convenience of persons who frequently travel, and is contained in a fish-skin case about seven inches long, four inches and an half broad, and two inches deep, and is the most complete instrument of the sort.

TO USE THIS MICROSCOPE.

As in the former one, place the slider-holder K, with a slider of objects in it, in the stage N I S; move the arm C D, in its socket, so that a mark on the side is brought to the edge of the socket; then turn the arm till the magnifier is directly central over the object; look down the tube A B, and during that time, reflect the light strongly and clearly up into it from the mirror O below; and then, while you are looking through the body, gently turn the pinion at M to the right or left, till you see the object magnified in the most distinct and well-defined manner. Attending properly to this mode is the only care necessary to use any microscope whatsoever; and for want of doing which, many a beginner finds a difficulty in using properly his instrument. For price, see the list at the end.

For opake objects, you take away the slider-holder, K; place on the stage either the concave glass, _s_, or the nippers, _b_; screw the concave speculum, _e_, to the arm, _a_, which place on the stage with the arm in the hole, I. The light is now to be reflected into this concave dish from one of the mirrors, O, below, and it will thus be strongly condensed upon the object. With this concave speculum any of the magnifiers in the wheel, P, may be used. When the single silver concave, _f_, is used, it is screwed to the arm C D, and the one, _e_, and arm, _a_, are not then applied.

For further directions for the management of microscopes, the light, &c. see Chap. IV. p. 129, and sequel.

A DESCRIPTION OF CULPEPER’S, OR THE COMMON THREE-PILLARED MICROSCOPE. Plate IV. Fig. 3.

The only recommendations of this original instrument are, its simple construction and lowness of price. It gives a pleasing view of the object. It is precluded by its form from some of the advantages of the two foregoing instruments, because both the stage and the mirror are confined. This microscope consists of a large exterior brass body, A B, supported on three brass scrolls, which are fixed to the stage F; the stage is supported by three larger scrolls that are screwed to the mahogany pedestal G H. There is a drawer in the pedestal which holds the apparatus. The concave mirror, I, is fitted to a socket in the center of the pedestal. The lower part, B, of the body forms an exterior tube, into which the upper part of the body, C, slides, and may be moved up or down by the hand, so as to bring the magnifiers which are screwed on at D, nearer to, or further from the object.

A LIST OF THE APPARATUS TO CULPEPER’S MICROSCOPE.

Five magnifiers, each fitted in a brass cell; one of these is seen screwed on at D. Six ivory sliders, _k_, five of them with objects; and a small ivory box, _m_, containing some spare talcs, and wires for them. A brass tube, N, to hold the concave speculum. A brass box, M, for the same speculum. A fish-pan, _c_. A set of glass tubes, _b_. A flat and a concave glass, both fitted to the stage. A brass cone, _g_, to exclude superfluous light; it applies at the under side of the stage, F. A brass box, _p_, with plane and concave glasses for living objects. A pair of forceps, _q_. A steel wire, _b_, with a pair of nippers at one end, a point at the other, and a small ivory cylinder, _h_, to fit on the pointed end of the nippers. A convex lens, E, moveable in a brass semicircle; this is affixed to a long brass pin, which fits into a hole, F, on the stage. The uses of the above apparatus have been sufficiently described in the preceding pages.

TO USE THIS MICROSCOPE.

Screw one of the five cells, which contains a magnifying lens, to the end, D, of the body; place the slider _i_ or _k_, with the objects, between the plates of the slider-holder, K. Then, to attain distinct vision and a pleasing view of the object, adjust the sliding body to the focus of the lens you are using, by moving the upper part, C, gently up and down while you are looking at the object, and regulate the light by the concave mirror, I, below. The image of the objects in this microscope is seen in a field of view of about six inches in diameter; but, in the improved ones before described, it is from about twelve to fifteen inches.

For opake objects, two additional pieces must be used; the first is a cylindrical tube of brass, represented at N, which fits on the cylindrical snout above D of the body: the second piece is the concave speculum, L; this is to be screwed to the lower end of the aforesaid tube. The upper edge of this tube should be made to coincide with the line which has the same number affixed to it as the magnifier you are using; that is, if you are making use of the magnifier marked 5, slide the tube to the circular line on the tube above D, that is marked also with No. 5.

The slider-holder, K, should be removed when you are going to view opake objects, and a plane glass should be placed on the stage in its stead to receive the object; or it may be placed on the nippers, _b_, the pin of which fits into the hole in the stage.

A DESCRIPTION OF MARTIN’S IMPROVED SOLAR MICROSCOPE, WHICH IS CONSTRUCTED TO EXHIBIT TRANSPARENT AND OPAKE OBJECTS. Plate V.

The solar microscope is generally supposed to afford the most entertainment, on account of the wonderful extent of its magnifying power, and the ease with which several persons may view each single object at the same time. The use of it was, however, confined for many years only to transparent objects. About the year 1774, Mr. B. Martin so far improved this instrument, as to render it applicable to opake, as well as to transparent objects, exhibiting the magnified image of either kind on a large screen. Treating of it himself, he says[34], “With this instrument all opake objects, whether of the animal, vegetable, or mineral kingdom, may be exhibited in great perfection, in all their native beauty; the lights and shades, the prominences and cavities, and all the varieties of different hues, teints, and colours, heightened by the reflection of the solar rays condensed upon them.” From its enlarged dimensions, transparent objects are also shewn with greater perfection than in the common solar microscope.

[34] Description and Use of an Opake Solar Microscope. 8vo. 1774.

Plate V. Fig. 1, represents the solar opake microscope, placed together for exhibiting opake objects.

Fig. 2, is that part called the single tooth and pinion microscope, which is used for shewing transparent objects; the cylindrical tube, Y, thereof, being made to fit into the tube E F, Fig. 1. It may be occasionally used as a hand single, or Wilson’s microscope, and for which purpose, the handle, _c_, is fitted by a screw to the body at _g_, and the tube, Y, screwed away.

Fig. 3, the slider which contains the six magnifiers; it fits into a dove-tail under P, Fig. 2, at the upper part of the microscope.

Fig. 4 represents a brass dove-tail slider, containing a small lens: it is called a condenser. There are three in number, marked 1 and 2, &c. corresponding to the number of the magnifiers used: they serve to condense the sun’s rays strongly upon the object, and enlarge the circle of light. They slide in at _h_, Fig. 2.

A B C D E F, Fig. 1, represents the body of the solar microscope; one part thereof, A B C D, is conical, the other, C D E F, is cylindrical. The cylindrical part receives the tube, G, of the opake object box, or the tube, Y, of the single microscope, Fig. 2. At the large end, A B, of the conical part there is a convex lens to receive the rays from the mirror, and refract them convergingly into the box, H I K L.

N O P is a brass frame which is fixed to the moveable circular plate, _a b c_; in this frame there is a plane mirror, to reflect the solar rays through the afore-mentioned lens. This mirror may be moved into the proper positions for reflecting the solar rays, by means of rack-work turned by the nuts Q and R. By the nut Q, it may be moved from right to left; it maybe elevated or depressed by the nut, R. _d_ _e_, two screws to fasten the microscope to a window-shutter, or a board fitted entirely before the window.

The box for opake objects is represented as open at H I K L; it contains a plane mirror, M, for reflecting the light that it receives from the large lens to the object, and thereby illuminating it; S is a screw to adjust this mirror to its proper angle for reflecting the light. V X, two tubes of brass, one sliding within the other, the exterior one in the box, H I K L; these carry two magnifying lenses: the interior tube is sometimes taken out, and the exterior one is then used by itself. Part of this tube may be seen in the plate as within the box, H I K L.

At H, is a brass plate, the back part of which is fixed to a tube, _h_, containing a spiral wire, which keeps the plate always bearing against the side, H, of the brass box H I K L. The sliders, with the opake objects, Fig. 5, pass between this plate and the side of the box; to apply which, the plate is to be drawn back by means of the nut, g. _k i_, a door to one side of the opake box, to be opened when adjusting the mirror, M.

The foregoing pieces constitute the several parts necessary for viewing opake objects. We shall now proceed to describe the single microscope, which is used for transparent objects; but, in order to examine these, the box, H I K L, must be first removed, and in its place we must insert the tube, Y, of the single microscope, Fig. 2, now to be explained.

Fig. 2 represents a large tooth and pinion microscope; at _m_, within the body of this microscope, are two thin plates that are to be separated, in order to let the ivory sliders, Fig. 7, pass between them; they are pressed together by a spiral spring, which bears up the under plate, and forces it against the upper one. The slider, Fig. 3, that contains the magnifiers, fits into a hole at _n_; any of the magnifiers may be placed before the object, by moving the aforesaid slider: when the magnifier is at the center of the hole P, a small spring falls into one of the notches which is on the side of the slider, Fig. 3. At _h_, slides a condenser, Fig. 4, for condensing the sun’s rays, and enlarging the field of view on the screen: the number must correspond with that of the magnifier used. This microscope is adjusted to the focus, while exhibiting the object, by turning the milled nut O.

APPARATUS TO THE OPAKE SOLAR MICROSCOPE.

The mirror O P, Fig. 1, and square plate, and the tubular body of the microscope, A F. The opake box and its tube, I K G. The tooth and pinion or single microscope, Fig. 2. The slider of magnifiers, Fig. 3. The megalascope magnifier, Fig. 6, fitted to P of Fig. 2. Six ivory sliders with transparent objects, Fig. 7. Twelve wood sliders with opake objects, and a brass frame to hold them, Fig. 5. A brass square-formed slider case, Fig. 8, to hold any animal, piece of ore, or other opake object, and is to be placed like the other slider at H, Fig. 1. A pair of nippers and point, Fig. 9, the pin, _a_, of which fits into the hole of the slider, Fig. 4, and holds before the magnifiers at P, Fig. 2, any small fly or other complete object to be magnified. A four-glass slider in a brass frame, Fig. 10, for any animalcula, &c. to be placed between the plates at _m_, Fig. 2. A set of glass fish tubes, Fig. 11. A pair of forceps, Fig. 12. Two brass nuts for the window-shutter or board, Fig. 13; and the two brass fastening screws, _d e_, Fig. 1, which may be either used with or without the above two nuts.

The figures on the plate are about half the original size, and the apparatus now made by Messrs. Jones packs into a case thirteen inches long, nine inches broad, and four inches deep. For price, see the list at the end.

TO USE THE SOLAR MICROSCOPE.

Make a round hole in a window-shutter or window-board, that is opposite to the meridian sun, or as nearly so as possible, a little larger than the circle _a b c_; pass the mirror, N O P, through this hole, and apply the square plate to the shutter; then mark with a pencil the places which correspond to the two holes through which the screws are to pass; take away the microscope, and bore two holes at the marked places, large enough to admit the milled screws, _d e_, to pass through them. These screws are to pass from the outside of the shutter, to go through it, and being then screwed into their respective holes in the square plate, they will, when screwed home, hold it fast against the inside of the shutter, and thus support the microscope.

Another way, and perhaps more convenient, is to previously screw the two brass nuts, Fig. 13, to the shutter or window-board, at the inside at a suitable distance, to receive the two milled screws; these nuts will always be ready for use, and the operator may in a minute, within his room, fasten the plate, _a b c_, to the shutter by the two milled screws, being placed contrarywise.

Screw the conical tube, A B C D, to the circle, _a b c_, and then slide the tube, G, of the opake box into the cylindrical part, C D E F, of the body, if opake objects are to be examined; but if transparent objects are intended to be shewn, then place the tube Y, Fig. 2, within the tube C D E F. The room is to be darkened as much as possible, that no light may enter but what passes through the body of the microscope; for, on this circumstance, together with the brightness of the sun, the perfection and distinctness of the image in a great measure depend.

We shall first consider the microscope as going TO BE USED FOR OPAKE OBJECTS. Adjust the mirror, N O P, so as to receive the solar rays, by means of the two finger-screws or nuts, Q, R; the first, Q, turns the mirror to the right or left; the second, R, raises or depresses it: this you are to do, till you have reflected the sun’s light through the lens at A B, strongly upon a white-paper screen or cloth, from four to eight feet square (about the latter dimensions for transparent objects) placed from about five to eight feet distance from the window, and formed thereon a round spot of light: a white wainscot or wall at a suitable distance answers very well. An unexperienced observer will find it more convenient to obtain the light by first forming this spot, before he puts on either the opake box, or the tooth and pinion microscope, Fig. 2.

Now apply the opake box, and place the object between the plates at H; open the door, _k i_, and adjust the mirror, M, till you see you have illuminated the object strongly. If you cannot effect this by the screw S, you must move the screws Q, R, in order to get the light reflected strongly from the mirror, N O P, on the mirror M; without which the latter cannot illuminate the object. The object being strongly illuminated, shut the door, _k i_, and a distinct view of the object will soon be obtained on your screen, by adjusting the tubes V X, with the magnifiers, which is effected by moving them backwards or forwards.

A perfectly round spot of light cannot always be procured in northern latitudes, the altitude of the sun being often too low; neither can it be obtained when the sun is directly perpendicular to the front of the room. As the sun is continually changing its place, it will be necessary, in order to keep his rays full upon the object, to keep them continually directed through the axis of the instrument, by turning the two screws Q and R.

To view transparent objects, remove the opake box, and insert the tube, Y, of Fig. 2, in its place; put the slider, Fig. 3, into its place at _n_, a condenser, Fig. 4, at _h_, and the slider with the objects between the plates at _m_; then adjust the mirror, N O P, as before directed, by the screws, Q, R, so that the light may pass through the object; regulate the focus of the magnifier by the pinion, O. The most pleasing magnifiers in use are the fourth and fifth. The size of the object is generally from four to eight feet, and may be increased or diminished by altering the distance of the screen from the microscope; five or six feet is a convenient distance.

The effect by this sort of microscope is stupendous, and never fails to excite wonder in an observer at the first view, in seeing a flea, &c. augmented in appearance to SEVEN, EIGHT, or even TEN FEET in length, with all its colours, motions, and animal functions, distinctly and beautifully exhibited.

TO EXAMINE TRANSPARENT OBJECTS OF A LARGER SIZE, or to render the instrument what is usually called a megalascope, take out the slider, Fig. 3, from its place at _n_; screw the cell and lens, Fig. 6, into the hole at P, Fig. 2; remove the glass which is placed at _h_, and regulate the light and focus agreeable to the foregoing directions.

At C D, is placed a lens for increasing the density of the rays, for the purpose of burning or melting any fusible substance; this lens must be removed in most cases, lest the objects should be burnt. The intensity of the light is also varied by moving the tube G, and Fig. 2, Y, inwards or outwards.

DESCRIPTION OF THE TRANSPARENT SOLAR MICROSCOPE AND APPARATUS. Plate VI. Fig. 4, to 14.

The foregoing description will, in great part, answer for this microscope; but, the dimensions, apparatus, &c. varying in a small degree from the preceding, a distinct description here, may be acceptable to those, who possess this sort of microscope only.