Page:Cyclopaedia, Chambers - Volume 2.djvu/760

 S P E

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S P E

the Specks are mere Delufions and Appearances, which God impreffes on our Senfes.. See Absolute Accident.

Species, in Commerce, are the feveral 'Pieces, of Gold, Silver, Copper, (yc. which having pafs'd their full Prepara- tion, and Coinage, are currant in Public. See Coin.

Species decried, or cried daw, are fuch as the Prince has forbidden to be received in Payment.

Light Species, are thofe that fall ihort of the Weight pre- ferred by Law.

Fa/fe Species, are thofe of different Metal from what they Jhould be, gfc.

Species, in Algebra, are the Symbols, or Characters, whereby the Quantities are represented. See Character.

SPECIFIC, in Philofophy, that which is proper, or pe- culiar to any thing ; that characterizes it, and diftmguiffies it from every other Thing.

Thus the attrafling of Iron is Specific to the Load-ftone, or a Specific Property of the Load-ftone.

, A juft Definition fhould contain the fpecific Notion of the Thing defined, or that which fpecifies and" diftinguifhes it from every thing elfe. Sec Definition.

Specific, in Medicine, a Remedy, whole Virtue and Effect is peculiarly adapted to fome certain Difeafe ; is ade- quate thereto ; and exerts its whole Force immediately there- on.

Thus Quinquina, or the Jefuits Bark, is held a Specific for intermitting Fevers or Agues ; Mercury for the Venereal Difeafe, ££c. See Quinquina.

Authors make mention of three Kinds of Specific Me- dicines.

I ° Such as are eminently and particularly friendly to this or that Part, as the Heart, the Lungs, the Brain, the Sto- mach, &c.

2° Such as feem to attract, expell, or evacuate fome de- terminate Humour, by a kind of Specific Power they are endowed withal ; as Jalap is fuppofed to purge watery Hu- mors, Rhubarb, Bile, £$c.

And, 1°, Such as remove the Caufe of a Difeafe, by fome fudden Property, without our knowing how or why ; or the Manner of whofe Operations we are entirely ignorant of, and have only learnt their Effects by Experience.

In the Ufe ot thefe laft, there is no Enquiry into the Nature of theDifeafe ; no regardhad to the Symptoms or Phenomena : Nor is the Medicine to be at all adapted to the particular Circumffances thereof. All that we regard, is the Name of the Difeafe, and that of the Remedy : As, immediately, upon finding an intermitting Fever, we preicribe the Bark; to afiuage Fain, Opium ; to expel Poifon, fome particular An- tidote.

A Specific Medicine, therefore, ftands in Oppofition to a Scientific or Methodic Medicine. See Medicine.

Specific Gravity, in Hydroftaticks, that Gravity, or Weight peculiar to each Specks, or Kind of natural Body ;and whereby it is diftinguifhed from all other Kinds. See Weight.

In this Senfe, a Body is laid to be fpecifically Heavier than another, when under the fame Bulk it contains a greater Weight than that other ; and that other, is laid to be fpe- cifically Lighter than the Firft. Thus, if there be two equal Spheres, each a Foot in Diameter ; only the one Wood, the other Lead : Since the Leaden one is found heavier than the Wooden one, it is laid to be fpecifically or in Speck, Heavier, and the Wooden one fpecifically Lighter.

This kind of Gravity, fome call relative Gravity's in op- pofition to abfolute Gravity, which increafes in Proportion to the Quantity or Mais of the Body. SeeGRAVlTY.

Zones of the Specific Gravity and Levity of "Bodies.

1. If two Bodies be equal in Bulk, their fpecific Gravities are, to each other, as their abfolute Gravities. Thus a Body is faid to be twice as heavy, fpecifically, as an- other," if it have twice its Gravity under the fame Bulk

Hence, the fpecific Gravities of equal Bodies, are as their Denfities. See Density.

2. The specific Gravities of Bodies of the fame Weight, are in a reciprocal Ratioof their Bulks. Hence, theMaffes of two Bodies of the lame Weight, are in a reciprocal Ratio of their Bulks.

3. The jpecific Gravities of two Bodies are, in a Ratio, compounded of the direct Ratio of the abfolute Gravities, and the reciprocal one of their Bulks.

Hence, again, the ffiecific Gravities are as the Denfities.

4. A Yse&y fpecifically heavier than a Fluid, lofes 16 much of its Weight therein, as is equal to a Quantity of the Fluid of the fame Bulk.

For, fuppofe a Cubic Inch of Lead immerged in Water : a Cubic Inch of Water will, thereby, be expell'd from its Place : But the Weight of this Water was futtained by the Refiftance of the ambient Water. Therefore, fuch a Part of the Weight of the leaden Cube, muft be fuffained by the Refiftance of the ambient Water, as is equal to the Weight of the Water expell'd. The Gravity of the Body immcrg'd, therefore, muft be diminiflied by ib much.

Hence, i°, Since a Fluid fpecifically heavier, has a greater Weight, in the lame Bulk, than a lighter 5 the fame Body will lofe a greater Part of its Weight in a Fluid, fpecifically heavier than in a lighter ; and therefore it weighs more in a lighter than a heavier. " •

2° Equal homogeneous Bodies weighing equally in Ai> lofe their Equifibrium, if one of them be immerg'd in a heavier Fluid j the other in a lighter.

3 Since the fpecific Gravities are as the abfolute Gravities under the fame Bulk ; the fpecific Gravity of the Fluid, will be to the Gravity of the Body immerged ; as the Part of the Weight loft by the Solid, to the whole Weight.

4, Two Solids equal in Bulk, lofe the fame Weight in the fame Fluid ; but the Weight of the fpecifically heavier Body, is greater than that ot the fpecifically lighter j therefore, the fpecifically lighter, lofes a greater Part of its Weight, than the fpecifically heavier. «-

4. Since the Bulks of Bodies equal in Weight, are re- ciprocally as the fpecific Gravities ; the fpecifically lighter, lofes more Weight in the fame Fluid than the heavier j wherefore, if they be in Equilibrio in one Fluid ; they will not be fo in another ; but the fpecifically heavier, will prepon- derate, and that the more as the Fluid is denfer.

j. The Specific Gravities of Fluids, are as the Weights loft by the fame Solid immerged in the fame,

'To find the Specific Gravity of any Fluids.

On one Arm of a Balance fufpend a leaden Globe ; and to the other, fallen a Weight, which is in Equilibrium there- with in the Air. Immerge the Globe fucceflively in the fe- veral Fluids, whofe fpecific Gravities are to be determined, " and obferve the Weight which balances it in each. Thefe feveral Weights, fubtracfed, feverally, from the firft Weight, the Remainders are the Parts of the Weight loft in each Fluid. Whence the Ratio of the fpecific Gravity of the Fluids isfeen. See Hydrostatical 'Balance.

Hence, as the Denfities are as the fpecific Gravities ; we find the Ratio of the Denfities of the Fluids at the fame time.

This Problem is of the utmoft Ufe ; as by it, the Degree of Purity or Goodnefs of Fluids, is eafily found ; a Thing, not only of Service in Natural Philofophy ; but alfo in com- mon Life, and in the Pract ice of Phyfic.

At different Seafons of the Tear, the fpecific Gravities of the fame Fluids, are found different. Joan. Cafp. Eifench- midius, in his Difquijitio Nova de Pcnderibus, &c. gives us Variety of Experiments relating hereto : The principal where- of, to fave the Trouble of too frequent Experiments, we fhall here fubjoin.

Table of Specific Gravities of feveral Fluids.

A Cubic Inch Paris

In Summer

Meafure.

0. D

G.

Of Mercury

7 1

66

Oil of Vitriol

7

59

Spirir of Vitriol

5

33

Spirit of Nitre

6

24

Spirit of Salt

5

49

Aquafortis

6

23

Vinegar

5

15

Diftill'd Vinegar

5

1 1

Burgundy Wine

4

67

Spirit of Wine

4

3J

Pale Ale

5

Brown Ale

5

2

Cows Milk

5

20

Goats Milk

5

24

Urine

5

■ 4

Spirit of Urine

5

45

Oil of Tartar

7

17

Oil of Olives

4

53

Oil of Turpentine

4

39

Sea Water

6

12

River Water

5

10

Spring Water

5

11

Diftill'd Water

5

8

In Winter

0. 2)

Sj

7 2

14


 * 7

7'

5

38

6

44

5

55

6

35

5

21

5

IS

4

75

4

42

5

9

5

7

5

25

5

28

5

19

5

53

7

43

Is froze in Winter

4

46

6

j8

5

'3

5

"4

5

11

That the fpecific Gravity may be found the more ac- curately j the Weight of the Thread not immerged in the Fluid, is to be iubrra&ed from the Weight of the Solid in Air; and the Force neceflary to make the Thread fiibfide (if it be fpecifically ligbtqr) is be to added to the Weight loft. But if the Thread that fultains the Solid be heavier than the Fluid ; the whole Weight of the Thread in the Air is to be fubtrafted from the Weight of the Solid in Air ; and the Weight the Thread lofes from the Weight loft in the Fluid. Indeed, this Precaution may be fpared, if in examining the fpecific Gravity of feveral Fluids, Care be taken that the fame Thread be immersed to the fame Depth in each.

1 *.To