Page:Cyclopaedia, Chambers - Volume 2.djvu/208

 MIR

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MIS

VII. If an Object be placed between a concave Mtr- rour and its Focus, its Image will appear behind the Mtr- rour, in an ere ct but inverted Situation.

VIII. If an Object A B, (i%. jtf.} be 'placed between the Focus and the Centre, its Image E F will appear in- verted, and in the open Air, beyond the Centre, the Eye being placed beyond the Centre.

IX. If an Object E F be placed beyond the Centre C, and the Eye likewiie beyond the Centre, the Image will appear inverted in the open Air between the Centre and the Focus.

Hence, the inverted Images of Objects placed beyond the Centre, are reflected by a, concave Mirrour, erect, and may be received on a Paper apply'd between the Centre and the Focus, efpecially if the Room be dark : if the Object EF be further diilant from the Centre than is the Focus, the Image will be lefs than the Object.

On this Principle, concave Mirrours, efpecially thofe which are Segments of large Spheres, and are capable of reflecting intire Objects, exhibit many pleafing Pheno- mena. Thus, if a Man flour ifh. a Sword againlt the Mir- rour, another comes out thereof, and meets him with the fame Motions; and the Image of his Head coming out of the Mtrrour, if he ilrikc it with his real Sword, the ima- ginary Sword will /hike his real Head. If he it retch out his Hand, another Hand will be EtretcE'd out of rhe Mir- rour, and meet it at a great dittance in the open Air, J°£c.

And on the fame Principle are built Catoptric Ciitulc, which when look'd into, exhibit Images vatiiy bigger than the Cheft. See Catoptric Gftula.

X. The Image of a right Line perpendicular to a concave Mtrrour, is a right Line; but all oblique or parallel Lines are concave.

Cylindrical, Conical, Parabolical, and Ell'ptical Mirbours, or Specula, are thofe terminated by a Surface reflectively Cylindrical, Conical, Parabolical, and Spheroidical. See Cylinder, Cone, Parabola, ££c.

To prepare, or make Cylindrical, Conical, Parabolical, Ellipti- cal, and Hyperbolical Mirrours.

For Cylindrical and Conical Mirrours, it they are to be of Glafs, the Method of preparing 'em is the fame as that al- ready laid down for convex Mirrours.

If of Metal, they are to be made after the manner of Coticaze Mirrours, only that the clay Moulds there defcribed, require other Wooden ones of theFigure of the Mrrour.

Fox Elliptical, Parabolical, and Hyperbolical Mirrours, the- Mould is to be thus prepared. On a Wooden or Brazen Plane or Table, defcribe the Figure of an BUipfts, A B, {Fig. 37.) a Parabola, aran Hyperbola C D, (fisr.38 ) after the manner taught under thofe heads; which done, cut out the Figure from the Plane with all the Accuracy ima- ginable.

To the Elliptic Figure, fit an Axis, as E F, with two Fulcra to full a in it, f£c. and ro move it. Lay a Quantity of the Lay abovedefcribed under it 5 and turn about the Axis by the Handle, till the Plane A B have turn'd, or im- prefs'd the Elliptical Figure exactly thereon. ■ The Axis of the Parabolical, or Hyperbolical Figure CD, is to be fix'd at the Vertex in fuch manner as it may always remain Erect. This to be turn'd about as above, till it have given its own Figure to the Clay apply'd about it.

The part of the Mould thus form'd, is to be dry'd, and either fmcar'dover with Fat, or fprinkled withBrick- Duft. Then a convex Mould to be made, by putting a Quantity of the fame Clay into the Cavity thus form'd. This latter is call'd the Male, as the former the Female Mould.

The Male Mould being well dried, is to be apply'd within the Female; in fuch manner as only to leave the intended Thicknefs of the Mirrour between them. The reft as for concave Mirrours.

Thefe Mirrours are not made without the utmoft diffi- culty 5 by reafon, be the Moulds ever fo juft, the Figure of the Mirrour is apt to be damaged in the Grinding.

Phenomena, or Properties of Cylindrical Mirrours.

I. The Dimenfions of Objects correfponding length-wife to the Mirrour, are not much chang'd 5 but thofe corre- fponding breadth-wife, have their Figuresalter'd, and their Dimenfions leffen'd fomuch the more, as they are further from the Mtrrour : Whence arifes a very great Dillortion.

II. If the Plane of Reflexion cut the cylindric Mtrrour thro* the Axis, the Reflexion is performed in the fame man- ner, as in a plain Mtrrour; if it cut it parallel to the Bafe, the Reflexion happens in the fame manner as in a fpherical Mtrrour; if, laftly, it cut it obliquely, or be oblique to its Bafe, the Reflexion is the fame as in an Elliptic Mirrouv.

Hence, as the Plane of Reflexion never pafTes through the Axis of the Mirrour, except when the Eye and Ob- jective-Lme are in the fame plane 5 nor parallel to the Bale, except when the radiant Point and the Eye are at the fame height : The Reflexion in a Cylindrical M'rrour is ufually the fame as in an Elliptic one.

III. If a hollow cylindric Mirrour be oppofrd directly to the Sun, inllead of a Focus of a Point, the Rays will be reflected into a lucid Line parallel to its Axis, at a diitance fomewhat lefs than a fourth pare of its Diameter.

Hence arifes a Method of Drawing Jnamarphofes, i.e. wild deformed Figures on a Plane, which appear tfeautiful and well- proportion 'd when view'd in a cylindrical Mir- rour. See Anamorphosis.

FotE'!pt!c, Parabolic, Conic, and Pyramidal Mirrours, .\vq are not pouch acquainted with their Properties : Only that,

In the Firft, if a Ray flrike on it from one of its Fo- cus's, it is reflected into the other : So that a lighted Candie being placed in one, its Light will be collected in the orher.

That the Second, inafmuch as all the Rays they reflect meet in one Point, make the bed: Burning-Glaffes of all others.

And, Lailly, that wild irregular Figures may be fo drawn on a Plane, as that the Eye being placed over the Axis of the two lad, tht y /hall appear beautiful and well- proportion'd. See Anamorphosis.

MIS, a Particle prefix'd to divers Terms, particularly Law-Terms; denoting fome Fault, or Defect,

As in Mifprifian; Mifdicere, to fcandaiize one; Mfdocere, to teach amifs, £& See Misprision, gfc.

MISANTHROPY, a general Hatred to Man, and Man- kind : In oppolltion to Philanthropy. See Philanthro- py.

The Word comes from the Greek turns, Odium, Hatred; and ai>0£<rj©-, Homo, Man.

MISAVENTURE, or Misadventure, in Law, is ufed by Britton, &c. in an efpecial Signification, for the killing a Man partly by Negligence, and parrly by Chances As if a Pcrfon, thinking no harm, carelefly throws a Stone, or /hoots an Arrow, wherewith he kills another; in this cafe he commits no Felony, but only lofes his Goods, and has a Pardon of courfe for his Life. See Homi- cide.

Statwford diiVmgulfhes between Aventure and Mifaventttre, The firit he makes to be meer Chance; as if a Man be- ing upon, or near the Water, be taken with fome fudden Sickneis, and fo fall in, and be drown'd; or into the Fire 8 and be burnt.

Mifaz-enture, according to him, is when a Man comes to his Death by fome outward Violence, as the Fall of a Tree 5 the Running of a Cart-Wheel; the Stroke of a Horfe, &<.

Weft diflinguifhes Homicide into cafual and mix'd. The firft, when a Man is /lain by mere Accident, againft the mind of the Killer; as if the Ax fly off the Helve, and kill a Man : Which is the fame with Britton's Mifaventure.

MISCONTINUANCE, in Law, the fame with Difcon- t'nmance. See Discontinuance.

MISDEMEANOUR, an Offence, or Fault, particularly in the Execution of an Office.

Hi&h Crimes and Misdemeanours, are Offences of a heinous nature, next to High Treafon.

M1SE, a French Term, literally denoting Expence, or Disburfement, wrote in Latin Mifum or Mifa; and ufed in our Law- Books in divers Acceptations.

Firit, as an honorary Gift, or cuflomary Prefenr, where- with the People of Wales ufed to falute every new King and Prince of Wales at their Entrance upon the Principality. Antiently it was given in Cattle, Wine, Corn, %$c. for the Support of the Prince's Family; but when that Dominion was annex'd to the Entfijh Crown, the Gift was chang'd into Money. The County of Flint pays 2000 Marks, &c* for their Mtfe.

The County of Cheft er alfo pays a Mtfe or Tribute of 5000 Marks at the Change of every Owner of the faid Earldom, for the enjoying of the Privileges of that Pala- tinate. At Cheft er they have a Mi/e-Book, wherein every Town and Village in the County is rated what to pay to- ward the Mtfe.

Mifes are alfo taken for the Profits of Lands; fometimes for Taxes or Ta ill ages; and fometimes for Expences or Cofls : As pro Mifts £5? Cuftagm, for Coils and Charges in the Entries of Judgments, &c.

Mife k alfo a Term ufed in fpeaking of a Writ of Right. What in other Actions h call'd an Ijfue, in a Writ of Right is call'd a Mife or Me : fo that to join the Mife upon the Meer, is as much as to fay, to join IJ/ite on the meer Right, i.e. to join upon this Point, whether has the more Right, the Tenant or Demandant. See Issue, &c,

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