Page:Cyclopaedia, Chambers - Volume 2.djvu/193

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Tho the Ecclefiaftical Government was modell'd on the footofthe Political; yet in Gaul, and iome other Coun- tries, the diltinciions of Metropolitan and Primate were not obfcrved till very late. As the Frxf efi tts Gallia refided by turns at Treves, Vienne, Aries, and Lyons, he communi- cated the Rank and Dignity of Metropolitan and Primate to each of them in their turn; and yet none of the GaBckn Bifhops affumcd to themfelves the Rights, nor even the Precedence of Metropolitans. The Ep'fcopate level'd them all ; and asto Order, they had no regard, but to the Privi- leges of Seniority. This Equality lailed till the fifth Century, when the Conteft between the Bifhops o$.Vie.nne and Aries was fet on foot.

M. du Pin obferves, that in the Provinces of Africa, ex- cepting thofe whereof Carthage was the Metropolis, the place where the moil aged Bilhop refided became the Me- tropolis. The Reafon of which without doubt was this, that neither the Proconful, nor Pryfeclus ever fix'd their Refidence.

The fame Author obferves, that in Afia there were Me- tropolis's merely nominal, that is, which had no Suffragan, nor any Rights of Metropolitans. The Bifhops of Nice, Chakedon, and Berytus, had the Precedence of the other Bifhops, and the y \t\c o{ Metropolita7is, without any other Right or Prerogative befides the Honour of the Appellation; they themfelves being fubject to their Metropolitans.

A Metropolitan has the 'Privilege of Ordaining his Suf- fragans ; and Appeals from Sentences pafs'd by the Suffra- gans, are prefer 'd to the Metropolitan- See Bishop and Primate.

The Jefuit Camel had began a Hiflory ofmtropoies ; but dy'd e'er the fecond Volume was fintfhed.

MEZZANINE, a Term ufed by fome Architefts to fignify an Entrcfole. S~e Entresoce.

The Word is borrowed from the Italians, who call Mez- zanini thofe little Windows, lefs in height than breadth, which ferve to illuminate an Attic, or Entrefole.

MEZZO-T1NTO, in Sculpture, a particular manner of Engraving Figures on Copper. See Engraving.

Mezzo-Tmto is faid to have been firft invented by Prince Rupert ; and Mr. Evelyn, in his Hittory of Chalco- graphy, gives us a Head perform'd by that Prince in this way.

Tis pretty different from the common way of En- graving. To perform it, they rake, hatch, or punch the Surface of the Plate all over with a Knife, orlnitru- ment forthe purpofe; firft one way, then a-crofs, &c, till the face of the Plate be thus entirely furrow'd with Lines or Furrows c!ofe and as it were contiguous ro each other 5 fo that if an Impreflion were then taken from it, it would be one uniform blot or fmut.

This done, the Defign is drawn, or marked on the fame Face : after which, they proceed with Burnifhers, Scra- pers,^, to expunge and take out the Dents or Furrows in all the parts where the Lights of the Piece are to be ; and that more or lefs, as the Lights are to be ikonger or fainter : leaving thofe parts black which are to represent the Sha- dows or Deepnings of the Draught.

MIASMA, from tuuiw, infuino, I infect; is made ufe of to fignify fuch Particles, or Atoms, as are fuppofed to arife from diilemper'd, putrifying, or poifonous Bodies, and to arte 3 People at a diilance. See Contagion.

MICHAELMAS, the Feaft of St. Michael the Arch- angel,, held on the 29th of September. See Quartern- Day.

MICROCOSM, a.GreekTevm literally fignifying Little World ; chiefly underftood of Man, who is fo called by way of Eminency, as being an Epitome of all that is won- derful in the great World, or Macrocofm. Sec Macro- cosm.

The Word is formed from the Greek pi *,&<;, parvus, little ; and x-orruot, Mundus, World.

MICROGRAPHIA, Micrography, a Defcription of the Parts, and Proportions of Objects, that arc too fmall to be viewed without the Afliftaiice of a Microfcope. See Microscope. Dr. Hook's Micrographia is in much efteem among the Curious.

The Word is compounded of fttK&f, parvus, and 3>£7?h, fcripth, defcript'o,

MICROMETER, an Agronomical Machine,' which by means of a very fine Skrew, ferves to meafure extremely fmall Dillances in the Heavens ; as the apparent Diameters of the Planets', £&. to a great degree of Accuracy. See

DiSTAN CE.

The Word comes from the Greek <«<x£?f, parvus, and «5T£9i', Menfura ; in regard a fmall Length, e.g. an Inch, is hereby divided into a vaft number of Parts, e.g. in fome, 2&00 ; and in others more.

'I here is fome Controverfy about the Invention of the Micrometer. Meff. Auzout and Picard have the Credit of it in common Fame ; as being the firft who pubtifhed it, in the Year 1666. But Mr. Tovmley, in the PhUofophical TranfaBiotis, reclaims it for one of our own Countrymen,

Mr. Gafcoyne. He relates, that from fotne fcarrer'd Papers and Letters of this Gentleman, he had learnr, that before our Civil Wars he had invented a Micrometer, of as much effect as that fince made by M. Auzout, and had made ufe of it for fome Years, not only in taking the Diameters of the Planets, and Diftances upon Land, but in determining other Matters of nice Importance in the Heavens; as the Moon's Diftance, &c.

Monf. de la Hire, in a Difcourfe on the ^ra of rhe Inven- tions of the Micrometer, Pendulum Clock, and Telefcope, read before the Royal Academy of Science?, in ijt%

Author, he oblerves, in his; OofervatioHs on SaturtfiKhtg f &cS publifhed in 1659, gives a Method of finding the Diame- ters of the Planets by means of a Telefcope, viz- by put- ting an Object, which he calls Yirgula, of a proper Bigncfs to take in the Diftance to be meafured, in the Focus of the Convex Objeet-Glafs: In this Cafe, fays he, the fmallefi Object will be feen very dillinctly, in that place of the Glafs. By fuch means, he adds, he meafured the Diame- ters of the Planets, as he there delivers them.

This Micrometer, M. de la Hire obferves, is fo very little different from that publifhed by the Marquifs deMalvafia, in his Ephemerides, three Years after, that they ought to be elleemed the fame ; and the Micrometer of the Marquifs differ'd yet lefs from that publifhed four years after his by Auzout and Picard. Hence M. de la Hire concludes, that 'tis to Ni..Hi:ygens the World is indebted for the Invention of the Micrometer : without taking any notice of the Claim of our Countryman, Mr. Gajcoyne, which is prior by many Years to any of them.

ConjlrvMion and Vfe of the Micrometer.

1. Woljius defcribes a Micrometer of a very eafy and fim- ple Structure ; firft contrived by Kirchius.

In the Focus of a Telefcope fir a Brafs or Iron Ring A B, (Tab. Astronomy, fig.n.) wi'h Female Screws diametri- cally oppofite 10 each other. Into thefe infert Male Screws C E and F B, of fuch Length, as that they may be turned in the Tube, fo as to touch each other. And with this In- ftrument very fmall Spaces in the Heavens may be accu- rately meafured.

For when any Objects, viewed thro' a Tube, appear con- tiguous to the Screws ; if thefe be turned till they juft touch two oppofite Points, whofe Diftance is to be meafured, it will be evident how many Threads of the Screw they are apart. To determine how many Seconds anfwer to each Thread ; applying the Tube towards the Heavens, turn the Screws, till they touch two Points, whofe Diftance is already accurately known ; and obferve the Number of Threads correfponding to that Interval. Thus, by the Rule of Three a Table may be made of the Seconds correfponding to the feveral Threads; by means whereof, without more ado, the Dillances of any Points may be determined.

2. The Structure of the Micrometer now chiefly in Ufe, with the Manner of fitting it to a Telefcope, and apply- ing it, is as follows :

A B Cg (Plate Astronomy, fig. \z.) is a Rectangular BrafsFrame; the Side AB being about three Inches long, and the SideBC, as likewife the oppofite Side A g, about fix Inches ; and each of the three Sides about *- of an Inch deep. The two oppofite Sides of this Frame are fcrewed to the Circular Plate, to be mentioned hereafter.

The Screw P, which hasexai5tly forty Threads in anTnch, being turned round, moves the Plate GDEF along two Grooves made near the Tops of the two oppofite Sides of the Frame ; and the Screw Q_having the fame number of Threads in an Inch as P, moves the Plate R N M Y along two Grooves, made near the bottom of the faid Frame, in the fame Direction as the former Plate moves, but with only half the Velocity of that other. Thefe Screws are turned both at once, and fo the Plates are moved along the fame way, by means of a Handle turning the endlefs Screw S, whofe Threads fall in between the Teeth of the Pinions on the Screws P and Ch And note, that two half Revolutions of the endlefs Screw S, carry the Screw P exactly once round.

The Screw P turns the Hand a faften'd thereto, over a hundred equal Divifions, made round the Limb of a circu- lar Plate, to which the above named two oppofite Sides of the Frame are fcrew'd at righr Angles. The Teeth of the Pinion on the Screw P, whole Number is 5, take into the Teeth of a Wheel on the back-fide of the circular Plate, whofe Number is 15. Again, on the Axis of this Wheel is a Pinion of two, which takes into the Teeth of another Wheel, moving about the Center of the circular Plate, on the out-fide thereof; having 50 Teeth. This laft Wheel moves the leffer Hand h once round the above mention'd circular Plate, in the ~s part of the Time the Hand a is moving round : For becaufethe Number of Teeth in the Pinion on the Screw P, are 5, and. the Number of Teeth of the Wheel this Pinion moves, are 20; therefore the

Screw