Page:Cyclopaedia, Chambers - Volume 2.djvu/862

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Spencer, in his Differtation on the Urim and Thummin, maintains the Word to be Cfraldee, and to Signify the fame with Seraphim ; the Chaldeans being frequently known to change the w into r\ that is, the / into t. He adds, that thofe Images were borrowed from the Amorhes, the Chal- deans or Syrians 5 and that the Serapis of the Egyptians is the fame thing with the Teraphim of the Chaldeans. See Selden. deltits Syriis.

THERIACA, Preachy in Medicine, a Name the An- cients have given to various Compositions, efteem'd good againft Poifbns 5 but now generally retrained to what, by way of DiftintStion, we fometimes call Theriaca Andromacbi. See Alexifharmachic.

This is a Compound of no lefs than 64 Drugs, prepared, pulverized and reduced, by means of Honey, into a liquid Eleauary.

The Bafis, or Foundation of the Composition, is Vipers Flefh. M. Charas has wrote a particular Hiftory of the Ani- mals, Plants and Minerals, which enter the Composition of this fam'd Remedy.

'Tis found foveraign againft the Bites of venomous Beafts, and in the Wind-cholic ; and is alfoufed in intermitting Fevers, and in Cafes requiring Per fpi rati v'es and Diaphoreticks $ alfo in continual Fevers, efpecially fuch as are malignant, and where the Pulfe is low and ticking ^ in the Small-pox and Meaftes : And, as moft of the Ingredients thereof, are very hot, for all Difeafes, where the natural Heat is weak and languid.

Andromachits, Nero's Phyfician, paffes for the Inventor of the "theriaca $ at leaf!:, 'twas he gave the firft Defcription thereof in Elegiac Verfes ; his Son did the fame in Profe, and TJe/ndcraies in Iambics.

Anciently, the 'Treacle made at Venice had all the Vogue ; and many Hill retain the ancient Prejudice j but 'tis now pre- pared at Montftellier, at ^Paris, and even at London., with as much Advantage as at Venice,

There is another vulgar kind of Theriaca, calPd TJiatejJk- yon, becaufe only conflftirig of four Ingredients.

'Treacle Water and Treacle Vinegar are found good Prefer- vatives againft putrid Air, whether by being only fmelt at, or by rubbing the Wrifts, Temples, an'd Nofe therewith.

THERMAE, ancient Buildings, deftined for Bathing in. See Bath.

Among the nobleft Monuments of ancient Rome are reckon d the Therms or Baths of T)ioclefian.

Among us, 2^/77^ is reftrain'd to fuch Baths as arc hot,

The Word is form'd from the Greek, ■Ssp//©-, hot.

Thetmtf-, 'tis commonly argued, owe their Heat to a Col- luctation, or Effervefcence of the Minerals in them. Though Dr. Wcodivard afcribes it to the fubterraneous Heat, or Fire which communicates with them by fomc Spiracle or Canal whereby a greater Quantity of Heat is derived thither, than to ordinary'Springs. See Mineral and Water.

THERMOMETER, Thermometrum, an Inftrument Shewing, or rather meafuring, the Increafe and Decreafe of the Heat and Cold of the Air. See Heat, Air, &c.

The Thermometer and Thermofcope, are ordinarily ac- counted the fame thing ; Woljkts, however, makes a Difference 5 and Shews that what we call Thermometers, are, in reality, no more than Thermofcopes. Sec Thermoscope.

There are various Kinds of Thermometers ; the Conftrucf i- ons, Defe&s, Theories, &c. whereof, are as follow :

Conjtrttblion of a Thermometer, depending on the RarefaBkn of the Air.

In a Tube B C, (Tab. Pneumaticks Fig. 3. ) to which is faften'd a Glafs Ball AB, is put a Quantity of common Water mix'd with Aqua Regia, to prevent its freezing; and the Mixture ting'd withaSolution of Vitriol to 'give it a Greennefs. In filling the Tube, Care is taken that there be fo much Air left in the Ball and the Tube, as that when at its greateft: Con- denfation in the middle of Winter, it may juft fill the Ball 5 and yet in its greateft Rarefaction in Summer, may not drive all the Liquor out of the Tube. To the other Extreme of the Tube, is faften'd another Glafs Ball CD, open to the Air at D: On each Side the Tube is applied the Scale E F, divided into any Number of equal Parts.

Now, as the ambient Air becomes warmer, the Air in the Ball and the Top of the Tube, expanding, will drive the Liquor into the lower Ball, and confequently its Surface will defcend 5 on the contrary, as the ambient Air grows colder, that in the Ball becoming condenfed, the Liquor will afcend. Sec Rarefaction and Condensation.

ConftriicTion of the Mercurial Thermometer.

In the fame Manner, and with the fame Caution as before, put a little Quantity of Mercury, not exceeding the Bignefs of a Pea, into a Tube B C (Fig; 4. ) thus bent with Wreaths, that, taking up the lefs Height, it maybe the more manageable

and lefs liable to Harm ; divide this Tube into any Number of equal Parts to ferve for a Scale.

Here the Approaches of the Mercury towards the Ball A will fhew thelncreafes of the Degree of Heat. The Reafbn is the fame, as in the former.

The Deleft of both the Inftruments confifts in this, that they ate liable to be afted on by a doubleCaufe; For, not only a Decreafe of Heat, but alfo an Increafe of Weight of the Atmofphere, will make the Liquor rife in the one, and the Mercury in the other ; and, on the contrary, either an Increafe of Heat, or Decreafe of Weight of the Atmofphere will make it defcend. See Barometer.

ConftruBion of the Florentine or common Thermometer.

The Academics deldmento, considering the Inconveniences of the Thermometers juft defcribed ; attempted another, that Should meafure Heat and Cold, by the Rarefaction and Con- denfation of Spirit of Wine ^ though that be vaftly Jefs than that of Air 5 and, confequently, the Alterations in the Air like to be much lefs fenflble.

The Structure of their Thermometer is this : On fome little Pieces of Turmeric is pour'd a Quantity of rectified Spirit of Wine, which hereby receives a red Tin£ture 5 this done, the Spirit of Wine is filtrated again, and aoain through a brown Paper, that the coarfer Particles of°the Root may be feparatcd therefrom. With the Spirit thus- tinged and prepared, they fill a Glafs Ball A B (Fig. 5. ) with a Tube B C ; and that all the Spirit mayn't defcend in Winter into the Ball, 'tis convenient to put the Ball into a Lump of Snow, mix'd with Salt : Or, if the Inftrument be to be made in Summer, into Spring Water, impregnated with Salt-petre 5 that the condenfed Spirit may fhew how far it will retire in the extremeft Cold.

If it be ftill at too great a Diftance from the v Ball, part of it is to be taken out 5 and that the Tube mayn't be made longer than needs, 'tis convenient to immerge the Ball, fill'd. with its Spirit, in boiling Water ; and to mark the furtheft Point to which the Spirit then rifes.

At this Point the Tube is to be hermetically fcal'd, by the Flame of a Lamp ; and at the Sides, is to be added a Scale, as in the former Thermometer.

Now, Spirit of Wine rarifying and condenfing very con- siderably 5 as the Heat of the ambient Air increafes, the Spirit will dilate, and, confequently, will afcend in the Tube $ and as the Her.t decreafes, the Spirit will defcend 5 and the Degree or Quantity of Afcent and Defcent will be feen in the Scale. Yet as the Ratio of yefterdays Heat, to to-days, is not here- by difcovered, this Inftrument is not ftri&ly a Thermometer, no more than the former.

It is to be here obferved, i°. That as the natural Gravity of the Liquor makes it tend downwards ; fo it refifts its Afcent out of the Ball into the Tube ; and that the more, as it rifes higher : For which reafon, 'twere beft to have the Tube B C Horizontal.

2° Since there muft of Necefftty be fome Air left in the void Part of thcTube over the Liquor ; that Air, by its Elafti- city, will tend downwards, and, of confequence will reSIft the Rife of the Liquor, and be comprefs'd by it as it does rife: Its Elasticity, therefore, is thus increafed.

3 Since 'tis found from Experience, that a lefs Degree of Heat is communicated more eafily to the Spirit of Wine in the Ball, than a greater ; the Rarefactions of the Spirit of Wine are not proportionable to their Producing Caufes 5 efpecially fince a greater Degree of Heat finds more Liquor in the Tube than a lefs does, to which, notwithstanding, the Heat may be more eafily communicated, than to that ftagnatin? in the Ball.

On thefe Accounts, the Florentine Thermometer, though that commonly in Ufe, is far from being an accurate Meafure of Heat, &c. to which may be added what Dr. Halley ob- ferves in the c Philofophical 'TranfaBions, that he has learnt from thofe who have kept Spirit of Wine long, that it lofts Part of its expanfive Force, in Courfe of Time.

Various Methods have been propofed by various Authors, for finding a fix'd Point, or Degree of Heat and Cold, from, which to account the other Degrees.and adjuft the Scale $ that fo Obfervations made at the fame or different Times, in different Places, may be compared together.

Some note the Place the Liquor is at in Winter, when Water begins to freeze ; and again, that in Summer, when Butter placed near the Ball of the Microfcope, melts : The intermediate Space they divide into two equal Parts, the middle Point whereof anfwers, in their Graduation, to tem- perate Heat j and each Moiety they fub-divide into ten De- grees : Adding four other equal Degrees on each of the two Extremes. But this Method fuppofes the fame Degree of Heat and Cold, to anfwer to the freezing of all Water, and the melting of all Butter ; as alfo, that all Thermometers receive the" fame Impreffions from the fame Degree of Heat j all which are contrary to Experience.

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