Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/58

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and loofe fpikes of yellow flowers; thefe arc each divided into four very uneven fegments, the upper fegment is very large and is arched ; but the lower, and the tide ones are much fmaller and bend outwards. In the middle of the fegments there ftand two yellow ftamma, fuftaining each a round yel- low head ; the piitil arifes between thefe, and is of the fame colour, length, and thicknefs, with the ftamina. The cup is very fhort, confuting only of one leaf ; it is green and is divided in its upper part into two or three obtule fegments : The fruit is round and flefhy of the fize of a walnut, green while young, hut yellow when ripe, compofed of a Jarge quantity of a pale coloured pulp, furrounding a ftone of an oval figure divided into two cells ; in each of which is con- tained one^kernd or feed. Acl. Petropol. Vol. 8. p. 219.

MICRO COSMETER, a name given by Dolceus to an imagi- nary being, which he fuppofes to reiide in the brain, and direcl: all the actions.

MICROCOUSTlCSj the fame with microphones. See the article Microphones.

MICROPHONES, inftruments contrived to magnify fmall founds, as micro/copes do fmall objects.

MICROSCOPE {Cycl.) — compound Microfcopes fometimes ex- hibit a fallacious appearance, by reprefenting convex objects, concave, and vice verfa. See Philof. Tranf. N°. 476. p. 387. See fome accounts of the famous Leuwenhoek's Microfcopes in the Philofophical Tranfactions, N°. 380. & 458. Tiie folar or camera obfeura Micro/cope, and the Microfcope for opaque objects, are the invention of Dr. Luberkhun ; and have been executed by Mr. Cuff" in England. Phil. Tranf. N°. 458. p. 516, U 518.

Camera obfeura Microscope. See Solar Microscope.

Microscope for opaque objects. The Microfcope for opake ob- jects remedies the inconvenience of having the dark fide of an object next the eye : For by means of a concave fpecu- Ium of filver, highly polifhed, in whofe center a magni- fying lens is placed, the object is fo ftrongly illuminated, that it may be examined with eafe. Phil. Tranf. N°. 458, Sect. 9.

Solar Microscope. The Solar Microfcope is compofed of a tube,_a looking-glafs, a convex lens, and a Microfcope. The tube is brafs, near two inches in diameter, fixed in a circular collar of mahogany; which, turning round at pleafure, in a fquare frame, may be adjufted eafily to a hole in the fhutter of a window, in fuch a manner, that no light can pafs into the room but through the aforefaid tube. Faftcned to the frame by hinges, on the fide that goes without the window, is a looking-giafs, which, by means of a jointed brafs wire coming through the frame, may be moved either vertically or horizontally, to throw the fun's rays through the brafs tube into the darkened room. The end of the brafs tube with- out the fhutter has a convex lens, to collect the rays, and bring them to a focus; and on the end within the room, Wilfon's pocket Microfcope is fcrewed, with the object to be examined, applied to it in a Aider. The fun's rays being di- rected by the looking-glafs through the tube upon the object, the image or picture of the object is thrown diftinctly and beautifully upon a fcreen of white paper ; and may be mag- nified beyond the imagination of thofe who have not feen it. Phil. Tranf. N°. 458. Sect. 9.

MICROSCOPIC Oijfis. All things too minute to be viewed diftinctly by the naked eye, are proper objects for theMicro- fcope. Mr. Hook has diftinguifhed them to be exceeding fmall bodies, exceeding fmall pores, or exceeding fmall motions. Exceeding fmall bodies muft either be the parts of larger bo- dies, or things, the whole of which is exceedingly minute, fuch as fmall feeds, infects, fands, falts, &fc. Exceeding fmall pores are the interfaces between the folid parts of bodies, as in ftones, minerals, (hells, &c. or the mouths of minute veflels in vegetables, or the pores in the fkin, bones, and other parts of animals. Exceeding fmall motions are the movements of the feveral parts or members of minute animals, or the motion of the fluids, contained either in animal or vegetable bodies. Under one or other of thefe three heads, almoft every thing about us affords us matter of obfervation, and may conduce both to our amufement and inft ruction.

An examination of thefe objefls, however, fo as to difcover truth, requires a great deal of attention, care, and patience, with fome fkill and dexterity, to be acquired chiefly by practice, in the preparing, managing, and applying them to the Micro- fcope.

Whatever object offers itfelf as the fubjeft of our examina- tion, the fize, contexture, and nature of it, are firft to be confidered, in order to apply it to fuch glafles, and in fuch a manner as may fhew it beft. The firft ftep fhould always be to view the whole together, with fuch a magnifier as can take it in all at once, and after this the feveral parts of it may the more fitly be examined, whether remaining on the objea or feparated from it. The fmaller the parts are which are to be examined, the more powerful fhould be the magnifiers employed ; the tranfparency or opacity of the objea muff alfo be confidered, and the glafles employed accordingly fuited thereto, for a tranfparent object will bear a much greater magnifier than one which is opakc, fince the riearnefs that a

glafs muft be placed at, unavoidably darkens an' object if in ks own nature opake, and renders it verydifhculc to be feen, unlcfs by the help of the apparatus contrived for that purpofe, which has a filver fpeculum. Moft objects however become tranf- parent by being divided into extremely thin parts. Baker's Microf. p. 52.

The nature of the object alfo, whether it be alive or dead, a folid, or a fluid, an animal, a vegetable, or a mineral fub- ftance, mult likewife be confidered, and all the circumftances of it attended to, that we may apply it in the moft advantage- ous manner. If it be a living object, care muft be taken not to fquecze or injure it, that we may fee it in its natural irate and full perfection. If It be a fluid, and that too thick, it muft be diluted with water; and if too thin, we fhould let fome of its watery parts evaporate. Some fubffances are fkteft for obfervation when dry, others when moiffened ; fome when frefh, and others after they have been kept fome time. Light is the next thing to be taken care of, for on this the truth of all our obfervaiions depends ; and a very little obfer- vation wiil fhew how very different objects appear in one de- ' gree of it to what they do in another ; fo that every new object fhould be viewed in all degrees of light, from the greater! glare of biightnefs to perfect obfeurity, and that in all pofitions to each degree, till we hit upon the certain form and figure pf it. In many objects it is very difficult to diftin- guifh between a prominency and a deprefiion, a black fhadow and a black ftain, and in colour between a bright reflection and whitenefs. The eye of a fly in one kind of light appears like a lattice drilled full of holes, in the fun-fhine like a folid fubftance covered with golden nails, in one pofition like a furface covered with pyramids, in another with cones, and in others with ftill different fliapes.

The degree of light muft always be fuited to the object, if that be dark it muft be feen in a full and ftrong light ; but if tranfparent, the light fhould be proportion ably weak; for which reafon there is a contrivance both in the fingle and double Microfcope to cut off" abundance of the rays, when fuch tranfparent objects arc to be examined by the lar^eft magnifiers. The light of a candle for many objects, and efpecially for fuch as are very bright and tranfparent, and very minute, is preferable to day-light; for others a ferene day-light is beft ; but fun fbine is the worft light of all, for it is reflected from objects with fo much glare, and exhibits fuch gaudy colours, that nothing can be determined from it with any certainty. This however, is not to be extended to the folar, or camera obfeura Microfcope ; for in that nothing but fun-fhine can do, and the brighter that is the better ; but in that way we do not fee the object itfelf on which the fun- fhine is caft, but only the image or fhadow of it exhibited on a fcreen ; and therefore no confufion can arife from the glaring reflection of the fun's rays from the objea to the eye, which is the cafe in other Microfcopes. But then in that folar way we muft reft contented with viewing the true form and fliape of an objea, without expeaing to find its natural colour ; fince no fhadow can poflibly wear the colour of the body it reprefents,

Moft objeas require alfo fome management in order to bring them properly before the glafles. If they are flat and tranfparent and fuch as will not be injured by preflure, the belt way is to enclofe them in Aiders between two Mufcovy talcs or ifinglafles. This way the feathers of butterflies, the fcales of fifties, and the farinas of flowers may be very conveniently preferved, as alfo the parts of Infects, the whole bodies of minute ones, and a great number of other things. Thefe are to be kept in Aiders, each containing three, four, or more holes, and thefe muft not be filled promifcuoufly ; but all the things preferved in one Aider fhould be fuch as require one and the fame magnify- ing power to view them, that there may not be a necefiity of changing the glafles for every objea; and the Aiders fhould be marked with the number of the magnifier it is proper to be viewed with. In placing the objeas in the Aiders, it is always proper to have a fmall magnifier, of about an inch focus, in your hand, to examine and adjuft them by, before they are fixed down with the rings.

Small living objeas, fuch as lice, fleas, bugs, mites, minute fpiders, &c. may be placed between thefe talcs without in- juring them, if care be taken to lay on the brafs rings with- out prefling them down, and they will remain alive many weeks in this manner; but if they are too large to be treated thus, they fhould be either preferved between two concave glafles, or elfe viewed immediately, by holding them in the pliers, or flicking them on the point at the other end of that in ft rum en t.

If fluids come under examination, to difcover the animalcules in them, a fmall drop is to be taken with a hair pencil, or on the nib of a clean pen, and placed on a plate of glafs; and if they are too numerous to be thus feen diftinctly, fome wa- ter warmed by holding it in the mouth muft be added to the drop, and they will then feparate and be feen diftinctly. This is particularly neccflary in viewing the animalcules in the femen mafculinmn of all creatures ; which, tho' extremelv minute, are always fo numerous, that without this caution their true form can feldom be feen. But if we are to fee the falts in a fluid, the contrary method muft be obferved, and 3 the