THE
On the Centre of the Circle B, moves the Index C j which is a circular Plate, having a Compafs in the Middle, whole Meridian Line anfwers to the Fiducial Line an : at bb are fix'd two Pillars to fupport an Axis, which bears a Telescope like the former, whole Line of Collimation anfwers to the Fiducial Line aa.
At each End of either Telescope, is fix'd a plain Sight for the viewing nearer Objects, See Sight,
The Ends of the Index aa are cut circularly, to fit the Divifions of the Limb B ; and when that Limb is diago- nally divided, the Fiducial Line at one .End of the Index fliews the Degrees and Minutes upon the Limb. The whole Instrument is mounted with a Ball and Socket, upon a three- leg'd Staff.
Mod Theodolites have no Telefcopes, but only four plain Sights, two of them faiten'd on the Limb, and two on the Ends of the Index.
The Ufe of the Theodolite is abundantly fliewn in that of the 3V?/?/c/;T/t?$whichisonIyhaIf a 'theodolite. See Semicircle.
And in that of the pdain Table, which is occasionally made to be us'd as a Theodolite. See Plain Table.
Note, the Index and Compafs of the Theodolite, like- wife ferve for a Circumferentor, and are us'd as fuch. See
ClR CUM FEB. EN TOR.
THEOGONY, that Branch of the Heathen Theology, Which taught the Genealogy of their Gods. See God.
Heftod gives us the ancient Theogony, in a Poem under that Title. Among the ancient Writers, Dr. Burnet ob- ferves, Theogony and Cofimgony, fignify'd the fame Thing, In effect, the Generation ot the Gods of the ancient Per- Jians, Fire T Water, and Earth, is apparently no other than that of the primary Elements. See Cosmogeny 5 iee alio Chaos.
The Word is form'd from -3^?, God, and ppfy Geniture, Seed, Offspring.
THEOLOGY, call'd alfb Divinity, a Science which inftruftsus in the Knowledge of God, and divine Things ;or which has God, and the Things he has reveal'd, for its Object. See God and Divinity.
Theology is a Doftrine which mews us what we are to think of God, and of the Manner wherein he would be ferv'd. It is divided into two Branches, Natural, and Re- vealed or Supernatural. ^
Natural Theology, is the Knowledge we have of God from his Works, by the mere Light of Nature and Reafon, See Nature and Reason.
Supernatural Theology, is that which we learn from Reve- lation. See Revelation.
<Pofitwe Theology, is the Knowledge of the holy Scrip- tures, and of the Signification thereof, agreeable to the Opi- nions of the Fathers and Councils ; without the Aifittance of any Argumentation. Some will have it, that this ought to be call'd expofttive, not pofitive. See Positive.
Moral Theology, is that which teaches us the divine Laws relating to our Manners. See Moral.
Scholastic, or School Theology, is that which proceeds by Reafoning 5 or that derives the Knowledge of feveral divine Things from fome eitablifh'd Principles of Faith. See Scholastic.
The Ancients had a three-fold Theology ; the firft ^ivBaw, Mythic, fabulous, which flourifh'd among the Poets j and was chiefly employ'd in the Theogony, or Genealogy of the Gods. See Fable and Fabulous; fee alfb Theo- gony.
The fecond, Trotomw, 'Political, which was that chiefly embrac'd by the Politicians, Priefts, and People, as raoft fuitable and expedient to the Safety, Quiet, and Intereft of the State.
The third, tpvor/jw, Natural, chiefly cultivated by the Philofophers, as moll agreeable to Nature.
The Phyfical or Natural Theology acknowledg'd one only fupreme God $ to which it added Daemons, as Mediators between him and Man. See Daemon.
The Word is compounded of £eij, God, and Keys, Dif- courfe.
THEOLOGIUM, in the ancient Theater, was a Place, or little Stage, above that whereon the ordinary Actors ap- pear'd.
The Theologium was the Place where the Gods appear'd ; it alfo included the Machines whereon they deicended, and from which they fpoke. See Machine.
There was a Theologium requir'd for the Reprefentation of the Jjax of Sophocles, the Hippolitus of Euripides, tfc. Seal. Poet. lib. 1. cap. 1.
The Word is Latin, form'd from -JsS?, and \oy>t, Speech, Di(cour(e.
THEOPASCHlTEvS, a Seel of Hereticks, in the Vth Century, the Followers of PetYUs Fitllenfu, or "Peter the Fuller.
Their dininguimlns Do&rine was, That the whole Tri-
- nity fuffer'd in the Paflion of Jeftts Ckrift, Sec Patju-
PA55I4NS,
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T
H E
cyT* T y r ' mbrac ' d b y the Eunchean Monks of Scythia; who ufing their utruoft Efforts to make it obtain,
Cenfurf '""^ '^ Bc S imin S ° f ** f°'l°wi"g
and Conftantimfle, held in 483 : It was reviv'd in the IX th Century, and again condemn* in a Council at Rome, held in 862 under Pope Nicholas I.
F. men, in his Notes on ftamafcemsi fays, that the fame Error had been taught before Fullenfis, by Mollinarius, whofe Difciples were the firft that were call'd Theopatites, or Theopafchites. *
THEORBO, Theorba, a Mufical Inftrument, made in Form of a Lute ; except that it has two Necks, or Juga, the fecond and longer whereof fuftains the four laft Rows of C ™. which are to give the dcepeft Sounds. See Lute.
The Theorbo is an Inftrument, which for theft laft fixty or feventy Years, has fucceeded to the Lute, in the playing of thorough Baffes : Tis laid to have been invented in France by the Sieur Hotteman, and thence inttodue'd into Italy, &c.
The only Difference between the Theorbo and the Lute; is, that the former has eight Ba(s or thick Strings, twice as long as thofe of the Lute; which Excels of Length renders their Sound io exceedingly ibfr, and keeps it up fo long a Time, that 'tis no Wonder many prefer it to the Harpfi- chord itfelf. At leaft it has this Advantage, that it is eafily remov'd from Place to Place, fyc.
All its Strings are ufually fingle ; tho' there are fome who double the Bais Strings with a little Oflave, and the fimll Strings with an Unifon ; in which Cafe, bearing more Relem- blance to the Lute than the common Theorbo, the Italians call it the Archiluto or Arch-Lute.
The Word Theorbo is form'd from the French Theorbe; of the Italian Tiorba, which fignifies the lame Thing, and which feme will have the Name of the Inventor.
THEOREM, in the Mathematical Method, a Ptopofition which terminates in Theory, and which confiders the Pro- perties of Things already made, or done. See Theory: and Proposition.
Or, ftriftly, a Theorem is a Theoretical Propofition, de- due'd from leveral Definitions compat'd together. Thus, if a Triangle be compar'd with a Parallelogram ftanding on the lame Bale, and of the fame Altitude ; and, pattly, ftom their immediate Definitions, and, pattly, from other of their Properties already derermin'd, 'tis inferr'd, that the Parallelogram is double the Triangle ; that Propofition is a Theorem. See Definition, ig6.
There are two Things to be chiefly regarded in every Theorem, viz. the Propofition and the Demonftration : In the firft is exprefsd what agtees to fome certain Tiling under certain Conditions, and what does not. See Proposition.
In the latter, the Reafbns are laid down, by which the Underftanding comes to conceive that it does or does not agree thereto. See Demonstration.
Theorems are of various Kinds : Univerfal Theorem, is that which extends to any Quantity without Reftriflion, uni- verlally ; as this, That the Retlangle of the Sum and Diffe- rence of any tin Quantities, is equal to the 'Difference of their Squares.
•Particular -Theorem, is that which extends only to a par- ticulat Quantity.
Negative, is that which expreffes the Impoffibility of any Affettion ; as, That the Sum of two SiquaJrate Numbers cannot make a Square.
Local Theorem, is that which relates to a Surface • as That Triangles of the fame Safe and Altitude are equal. See Local.
A flane Theorem, is that which either relates to a Recti- linear Surface, or to one terminated by the Circumference of a Circle ; as, That all Angles in the fame Segment are equal Sec Plane.
A Solid Theorem, is that which confiders a Space termi- nated by a fblid Line ; that is, by any of the three Conic Seflions; e.gr. this, That if a right Line cut two Afymf to- uch 'Parabola's, its two Parts terminated by them Jbail be equal. See Solid.
A Reciprocal Theorem, is one whofe Converfe is true ; as 4 That if a Triangle have two equal Sides, it inuji have two equal Angles : The Converfe of which is true, That if it . have two equal Angles, it mufl have two equal Sides. See Reciprocal.
THEORETIC, Theoretical, or Theoric, fome- thing relating to Theory, or that terminates in Speculation - in which Senfc the Word ftands in Opposition to 'Practical. *
'Tis form'd from the Greek, &topa, I fee, I contemplate.
The Sciences are ordinarily divided into Theoretical as Theology, Fhilofophy,e?r. and Practical, as Medicine Law cifc. See Sciences.
In ancient Authors, Theoric Money was what was rais'd by Way of Tax on the People, to defray rhe Expences of The- atrical Reprefentations, and other Speflacles.
Thert
