Page:Cyclopaedia, Chambers - Volume 2.djvu/863

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Others advife the Ball of the Thermometer to be put in a Quantity of Snow and Salt, and the Point the Liquor is at to be noted. Thence, the Thermometer is to be removed into a deep Cave or Cellar, whither no external Air reaches ; fo that the Liquor receiving the Action of a temperate Air, may fhew the Degree of temperate Heat. Laftly, they divide the intermediate Space into 15, or more equal Parts, which they continue beyond each Extreme : But this Method is liable to the like Inconveniences as the former.

Dr. J/ri//eyaffumes That for a fix'd Degree of Heat, wherein Spirit of Wine begins to boil - t but there is Reafon to fufpecT: this, too, of being precarious : Though after him, M. Amon- iom retains the Degree of Heat, anfwering to boiling Water, for the graduating nis mercurial Thermometer. But as the different fpecific Gravities of Water, argue a Difference ot Mafs and Texture ; 'tis highly probable that Heat of all boiling Waters is not the fame: So that the Point is yet unde- termined.

THERMOSCOPE, an Inftrument {hewing the Changes happening in the Air, with refpecl: to Heat and Cold; See Air, Weather, l$c.

The Word Thermofcope is generally ufed indifferently, with that of thermometer. There is fome Difference, however, in the literal Import of the two Words ; the firft Signifying an Inftrument that /hews, or exhibits the Changes of Heat, &C. to the Eye ; form'd from -tappd. Heat, and gmz'w, video, I tee ; and the latter an Inftrument that meafiires thofe Changes ; from -S-eppt, Heat, and j«Wi t0 nneafure : on which Foun- dation the Thermometer ihould be a more accurate Tibet* mofcope, ($c.

This Difference the excellent Wolfius taking hold of, de- scribes all the Thermometers, inuie, as Tbermofcopes ; /hew- ing that none of them properly meafure the Chances of Heat, JSfc none of them do more than indicate the fame. Though their different Heights yefterday and to-day, /hew a Difference of Heat ; yet Since they don't difcovcr the Ratio of yefferday 's Heat to to-days, they are not, ftric~t.ly, Thermometers. See Thermometer.

In the AB& Eritdit. Zipf we have a Method of graduating the common Thermometers fo, as that the unequal Divisions thereof /hall correfpond to equal Degrees of Heat 5 whereby the Ratio of to-day's Heat to yeflerday's, will be meafured, and, confequently, the Thermofcope improved into a Ther- mometer

The Method is that of Car. Renaldimts, and is defcribed by the Leipfic Editors thus : Take a /lender Tube about four Palms long, with a Ball faflen'd to the fame ; pour into it Spirit of Wine, enough juft to fill the Ball when furrounded with Ice, and not a Drop over. In this State, feal the Orifice of the Tube Hermetically ; and provide fix VefTels, each capable of containing a Pound of Water, and fome- whatover; and into the firft, pour i\ Ounces of warm Water, into the fecond 10 Ounces, into the third 9, fyc, This done, immerge the Thermometer in the firft Veflel, and pour into it one Ounce of hot Water ; observing how high the Spirit rifes in the Tube, and noting the Point with Unity : then remove the Barometer into the fecond Veflel, into which is •pour'd two Ounces of hot Water, and note the Place the Spirit rifes to, with 2. By thus proceeding till the whole Pound of Water is fpenr, the Inftrument will be found divided into 12 Parts, denoting fo many Terms or Degrees of Heat : So that at 2, the Heat 1? double that at 1, at 3 triple, ££c.

But the Method, though plaufible, WbtjktS ihews is deceit- ful j and is built on falfe Suppositions : For it takes for granted, that we have one Degree of Heat, by adding one Ounce of hot to x 1 of cold Water; two Degrees, by adding two Ounces to 10, &c. It fupppofes that a fingle Degree ot Heat a£ls on the Spirit of Wine in the Ball with afingle Force, a double with a double Force, f$c. Laftly, it fuppofes, that if the Effecl be produced in the Thermometer by the Heat of the ambient Air which is here produced by the hot Water, the Air has the fame Degree of Heat with the Water.

But none of thefe Suppositions is true : For, as to the Firft ; allowing the Heat of the hot Water, equally diftri- buted through the Cold ; one Degree of Heat will then be diftributed through 11 Parts, two through 10, three through 9, &c. Taking, therefore, equal Bulks of the Water, e. gr. a twelfth Part of "each, the Heat will not be double in one, triple in another, quadruple in another, $§c.

The firft Supposition, therefore, is erroneous ; and fo is the Second : For neither is the Heat of the hot Water equably dif&fed throughout the cold ; nor does the Heat of the hot Water aft uniformly on the Spirit of Wine ; i. e. not with the fame Force, all the time of its Action.

For the third Supposition ; the Heat of the ambient Air acts not only on the Spirit of Wine in the Ball, but alfo on that in the Tube ; and therefore this, as well as that, will be changed.

THESEA, Thes^a, in Antiquity, Feafts celebrated by the Athenians, in Honour of Tbefeus. See Feast.

In fpight of the important Services that Hero had done his Country, in delivering it from a Shameful Tribute of fo

many Youths of either Sex, fent yearly to be devoured by the Minotaur in Crete (as the Fable has it) or fent as Slaves to Minos King of Crete, as the Hiftories have it ; from which he freed them, by overcoming Taurui, Minos's General : He was baniMi'd for fome time ; and retired to Scyro t under the Protection of Lycomedes, King of that I/land ; who Hew him out of Jeaioufy.

The Gods revenged this Treatment Tbefeus received from the Athenians, by afflicting them with a Famine, which the Oracle afTured them Should not ceafe, till they had avenged his Death.

Upon this, they flew Lycomedes, brought Thefemh Bones to Athens, placed them in a Temple erected to him, and appointed Thtfea to be held every Eighth Day of each Month ; wherein Large/Fes were diftributed to the People, and the Day fpent by the Rich in Feafting and Rejoicing

THESIS, in the Schools, a general Proposition, which a. Per/on advances, and offers to maintain.

The Word is pure Greek, &£?/<, Poftion. In the Colleges, 'tis frequent to have Placards, containing a Number of thefe Thefes.

There are Thefes in Theology, in Medicine, in Philofophy, in Law, £5?c. The maintaining a Tbejis, is a great Part of the Exercife a Student is to undergo for a Degree. See Degree.

Thesis, in Logic, $£ci every Proposition is divided into a Tkefis and Hypothecs : Thefts contains the Thing affirmed or denied ; and the Hypothefis the Conditions of the Affirma- tion or Negation : Thus, in Euclid, If a Triangle, and 'Pa- rallelogram have equal Safes and Altitudes, (is the Hypo- thefis) the Firft is half of the Second ; the Thefts. Se« Hypothesis;

THEURGY, Theuroia, a Name which the Ancients gave to that Part ot Magic, which we Sometimes call 'white Magic, or the white Art. See Magic.

The Word is form'd from the Greek, Qiot, God, and %?y>v. Work, q.d. the Art of doing divine Things, or Things which God alone can do ; or the Power of working extra- ordinary and Supernatural Things by lawful Means, as by Prayer, Invocation of God, &c.

Accordingly, thofe who have wrote of Magic in the gene- ral, divide it into three Parts; the firft whereof is call'd Theurgy, as operating by divine or cceleftial Means; the lecond, Natural Magic, performed by the Powers of Na- ture ; and the third, Necromancy, which proceeds by invok-. ing Damons. See Necromancy, &c.

THIGH, a Part of the Body of Men, Quadrupeds, and Birds, between the Leg and the Trunk. See Leg, ££?c.

The feveral Parts of the Thigh have different Names; The fore and upper Part is call'd the Groin, or Inguen; the Side, the Hanch, or Hip, Coxa, Coxendix ; the upper hind Part the Buttock-, Chtnis ; the lower and hind Part the Ham t "Poples, of pofi and plico, becau/e it bends backwards; and the fore Part the Knee, Genu, of the Greek pvv, Angle.

The Bone of the Thigh is the large/} and itrongeft in the whole human Body, as being to bear the whole Burthen thereof; whence its Name femur, of fero, I bear. See Femur.

THINKING, Cogitation, a general Name for any Aft or Operation of the Mind. See Mind and Thought.

Chauvin, with the Cartefians, will have Thinking to con- fift in a certain native inherent Motion or Agitation of the human Mind, whereof itfelf is confeious. — Native and Inherent, fince he conceives it no other than the very Eflencc of the Mind itfelf, or, at leaft, its principal and fundamen- tal Property ; - -An Agitation fvazt there is a new Modification or Change made m the Mind, which we fcarce know to con- ceive without Motion ; add, that the Origin and Etymology of the Word Cogitation, according to Varro and Feflus, im- plies as much ; ccgito being us'd for coagito.

When the M'nd turns its View inwards, upon itfelf, the firft Idea that -jffers, fays Mr. Lock, is Thinking ; wherein it obferves a g.eat Variety of Modifications, and thereof frames to it/elf diftinft Ideas : Thus the Perception annex'd to any Impreffion on the Body made by an external Objecl, is call'd Senfation. See Sensation.

When an Idea recurs without the Prefence of the Object, 'tis call'd Remembrance. See Memory.

When fought after hy the Mind, and brought again in View, 'tis call'd RecolleBmi. See Recollection.

When held there long under attentive Consideration, it is Contemplation. See Contemplation.

When Ideas float in the Mind without Regard or Re- flection, 'tis call'd a Revery: When they are taken exprefs Notice of, and, as it were, regifter'd in the Memory, it is Attention : And when the Mind fixss its View on any one Idea, and considers it on all Sides, it is Study and Intention. See Attention, Study, £f?c.

Thefe are the moft obvious Modes of Thinking; but. there are feveral others which we know of 5 and, doubrlefs, the Mind is capable of infinite others, whereof we have no Notion at all, See Mode.

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