Page:Cyclopaedia, Chambers - Volume 2.djvu/873

 T I M

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T I N

their Years by the coming and going away of Birds. See Periods.

Some Authors diftinguifh Time into Agronomical and Civil.

Agronomical Time, is that taken purely from the Motion of the heavenly Bodies, without any other regards.

CtvilTrme, isthe former Time accommodated to CivilUfes; and form'd and diftinguifh 'd into Tears, Months, T)ays, &c. See Day, Month, Week, Year, <&c.

In this Senfe, Time is the Subject of Chronology. See Chronology.

Time, in Mufic, is an Affection of Sound, whereby we denominate it long or port, with regard to its Continuity in the fame Degree of Tune. See Sound.

Time and Tune are the great Properties of Sound, on whofe Difference, or Proportions, Mufic depends : Each has has its feveral Charms; where the Time, or Duration of the Notes is equal, the Differences of Tune alone are capable to entertain us with endlefs Pleafure. See Tune.

And of the Power of Time alone, i.e. of the Pleafures arifing from the various Meafurcs of long and .fhort, fwift and flow 5 we have an Inftance in the Drum, which has no Difference of Notes, as to Tune. See Drum, Accent, £5?c.

Time, in Mufic, is confider'd, either with refpect to the abfolute Duration of the Notes, i. e. the Duration confider'd in every Note by itfelf, and meafured by fome external Motion foreign to the Mufic ; in refpect to which, the Compofhion is faid to be quick, or Jlo-w : or it is confider'd, with refpect to the relative Quantity or Proportion of the Notes compared with one another. See Note.

The Signs or Characters by which the Time of Notes is reprefented, are /hewn under the Article, Characters m Mufic j where the Names, Proportions, &c. are alio ex- prefs'd.

A Semi-breve, for Inftance, is mark'd to be equal to two Minims, a Minim to two Crotchets, a Crotchet to two Qua- vers, foon, and ftill in a duplicate Ratio, i.e. in the Ratio of 1 : j. Now, where the Notes refpecl: each other, thus, i, e. where they are in this Ratio 5 the Mufic is faid to be in Tiuple, i. e. double or common Time.

When the feveral Notes are Triple each other, or in the Ratio 3:1; that is, when the Scmi-breve is equal to three Minims, the Minim to three Crotchets, ££?c. the Mufic is faid to be trifle Time.

Now, to render this Part as fimple as poffible, the Propor- tions already flated among the Notes, are fix'd and invariable ; and to exprefs the Proportion of 3 : 1, a Point ( .) is added on the right Side any Note, which is deem'd equivalent to Half of it 5 and by this means a pointed Semi-breve O be- comes equal to three Minims, &c. fo of the reft.

From hence arife feveral other Ratios conftituting new Kinds of triple Time ; as 2:3 and 3 : 4, &c. but thefe Mr. Malcolm obferves, are of no real Service, and are not per- ceived without a painful Attention. For the Proportions of the Times of Notes, to afford us Pleafure, rauit be fuch as are not difficultly perceived 5 on which account, the only Ratios fit for Mufic, befides that of Equality, are the 'Double and Trifle.

Common or duple Time, is of two Species 5 the Firft, when every Meafure is equal to a Semi-breve, or its Value in any Combination of Notes of a lefler Quantity.

The Second, where every Bar is equal to a Minim, or its Value in lefler Notes. The Movements of this Kind of Meafure are various ; but there are Three common Diflincti- ons j the firft. flow, fignify'd at the beginning by the Mark C ; the fecond brisk, fignify'd by (£ j the third very quick, fignify'd by 3). ,

But what that flow, brisk and quick is, is very uncertain, and only to be learnt by Practice. The neareffc Meafure we know of, is to make a Quaver the Length of the Pulfe of a good Watch 5 then, a Crotchet will be equal to two Pulfes, a Minim to four, and the whole Meafure or Semi-breve to eight. This may be reputed the Meafure of brisk Time 5 for" the flow, 'tis as long again, and the quick, only half as long.

The whole Meafure, then, of common Time, is equal to a Semi-breve or a Minim : But thefe are varioufly fub-divided into Notes of lefs Quantities, Sec Measure.

Now to keep the Time equal, we make ufe of a Motion of the Hand or Foot, thus: Knowing the true Time of a Crotchet, we fhall fuppofe the Meafure or Bar a&ually fub- divided into four Crotchets for the firft Species of common Time 5 then the Half Meafure will be two Crotchets 5 there- - fore, the Hand or Foot being up, if we put it down with the very beginning of the firft Note or Crotchet, and then raifed with the Third ; and then down to begin the next Meafure : this is calfd beating of Time.

By Practice, we get a Habit of making this Motion very equal, and consequently of dividing the Meafure or Bar into equal Parts, up and down ; as alfo of taking all the Notes in the juft Proportion, fo as to begin and end them precifely with the beating. In the Meafure of two Crotchets, we beat down the firft, and the fecond up. Some call each Half of

the Meafure in common Time, a Time ; and fo they call this the Mode or Meafure of two Times, or the c Dtij>la Meafure.

Again, fbme mark the Meafure of two Crotchets with a 2or|, signifying it to be equal to two Notes, whereof four make a Semi- breve ; and fome mark it £ for Quavers.

For Trifle Time ; fee Triple Time,

Time in Fencing, There are three Kinds of Time ; that of the Sword ; that of the Foot, and that of the whole Body. All the Times that are perceived out of their Meafure, are only to be confider'd as Appeals or Feints, to deceive and amufe the Enemy.

Time in Grammar ~\ r Tense.

Time in Mecbanicks C c ee ) Motion.

Periodical Time in Aflronomy ( ^Period.

Equation of Time ) ^ Equation.

TiMK-Keefer, orTiM-E.-Meaft!re. See Chronometer.

TIN, a whitifh Metal, fofter than Silver, yet much harder than Lead. See Metal.

The Chymifts, &c. hold Tin an imperfect Metal, gene- rated of two different Seeds, viz. that of Silver and that of Lead ; which renders it a kind of Compound of both; and accordingly it is frequently found in Lead and Silver Mines.

Tin, however, has alfo its proper Mines, of which our Counties of Comwal and Devonfhire are an abundant Evi- dence : The greateft Part of the Tin confumed in Europe^ is procured from thence 5 and Cambden even fuppofes this Abundance of Tin in thofe two Provinces, to have given the original Denomination 'Britain to the whole Country. In the Syrian and Chaldee, Tin is calfd Bragmanac ; the Primitive whereof \s Bratman ot Britman, whence Britain.

The principal Characters or Properties of Tin, enumerated by Boerhaave, are, That it is the lighteft of all Metals j very little ductile or elaftic 5 the moft fufible and volatile of all Metals j fcarce difloluble by Acids, unlefs the weaker Sorts 5 and eafily and intimately mifcible with other Metals, the Ducti- lity whereof becomes diminifh'd by fuch Mixture.

The fame Author concludes, that Sulphur is a prevailing Ingredient in Tiii 7 and deduces feveral of its particular Pro- perties therefrom. He adds, that could the Metal be per- fectly purged of this heterogeneous Sulphur, 'tis probable it would be found no other than Silver.

Several Authors had before noted a great Conformity, in divers Particulars, between the two Metals ; as, that both, grow bitter when difTolved by Acids; that when fufed to- gether, there is fcarce any feparating them again, not even by Lead. Add, that Mr. Boyle and others, give us feveral Inftances of Silver being actually procured in confiderable Quantity from Tin Ore. See Silver.

Yet fome Naturalifts judge the Analogy greater between Tin and Lead ; and contend that Tin is only Lead, under a lefs Degree of Ccction ; but if there be fome Marks of Agreement between them, there are as many of Difagreement. The Calx of Lead, for inflance, eafily fufes and vitrifies, but that of Tin not without the laft Difficulty : If Tin and Lead be mix'd by a vehement Fire, a vehement Colluctation enfues, and they both run into a Calx : Add, that Tin is eafily revivified ; but Lead with great Labour. See Lead.

The Method of getting, preparing, &c. the Tin in the Comip Mines, much the belt and mofl confiderable in the World ; is given us in the < Philofofhical Tranfaffions.^

The working of the '27;2-Mines is very hard and difficult 5 not only by reafon of the great Depth which the Veins defcend to, even as low as jo Fathom ; but alfo becaufe the Rocks, through which PafTages are frequently to be cut, are often fo hard, that the Workman can't dig a Foot in a Week. Nor is the foft, fhaking Earth found in the 7m-Mines, much lefs inconvenient to the Workmen 5 both by reafon of fcetid, malignant Vapours it exhales, and of the Currents of Water often met withal therein : all thefe Difadvantages together render it impracticable for the Workmen to hold it above four Hours together.

The mineral Stones or Glebe being dug and drawn out of the Mine, is there broke into Pieces with large Iron Mallets ; then brought to a Stamping Mill, where 'tis ffill pounded fmaller with Stampers, much like thofe of Paper Mills ; and the Water paffing through it wafhes away the earthy Parts, leaving the Metallic ones behind : The Lotion is re- peated twice, to make the better Separation.

This done, they dry it in a Furnace on Iron Plates ; and grind it very fine in a Crafing Mill 5 then wafli it again 5 then dry ir : In this State, the metallic Matter is calTd Slock, or Black Tin.

To convert it into 77?;, i. e. into white Tin, they carry it to a Furnace or blowing Houfe ; where, by means of a Charcoal Fire, kept up by huge Bellows work'd with the Water, it is melted ; after it has pafs'd all thefe Preparations, and is become cold, they forge it ; which is the lafl Thing done to it in the Works,

The