936 
THEORY, 
the whole extant works of Theophrastus, is that of Dan. 
Heinsius, Greek and Latin, fol. Lugd. Bat. 1613. Of his 
“ History of Plants,” the most complete is that of Budaeus, 
Greek and Latin, fol. Amst. 1644. Among the most es¬ 
teemed editions of his “ Characters,” which are numerous, 
we may reckon those of Is. Casaubon, of Needham, with,the 
notes of Duport, Cantab. 1712, and of I. Fr. Fischer, 
Coburg. 1763. Ding. Laert. Brucker by Enfield. 
THEOPHYLACT, named Simocatta, a Greek histo¬ 
rian, a native of Greece, but of Egyptian origin, flourished 
about A. D. 612. His history of the reign of the emperor 
Maurice is comprehended in eight books, and terminates 
with the massacre of this prince and his children by Phocas. 
Casaubon reckons Simocatta one of the best of the later 
Greek historians. The work just mentioned was printed at 
the Louvre, in 1647, fol. and forms a part of the Byzantine 
historians. 
THEOPNEUSTA3 [©eorcveoxTat, formed from the Gr. of 
©so?, God , and wvevu, I breathe], an epithet given to en- 
thusiastical divines. 
THEOPOLIS, in Ancient Geography, a town of Gallia 
Narbonnensis, belonging to the Aventici, north-east of 
Forum Novum. 
THEOPROPRIA [0eo7rM:rna, formed from the Gr. of 
Gecf, God, and -srpora, I excel], a designation given to 
oracles. 
THEO'RBO, s. [tiorba, Italian ; tuorbe, Fr.] A large 
lute for playing a thorough bass, used by the Italians. Bailey. 
He wanted nothing but a song, 
And a well tun’d theorbo hung 
Upon a bough, to ease the pain 
His tugg’d ears suffer'd with a strain. Butler. 
THE’OREM, s. [ theoreme, Fr.; %eupyp.ci, Gr.] A position 
laid down as an acknowledged truth.—Having found this the 
head theorem, of all their discourses, who plead for the 
change of ecclesiastical government in England, we hold 
it necessary that the proofs thereof be weighed. Hooker. 
—A position proposed to be demonstrated. It is used by 
mathematicians in this sense as well as the other. Ma¬ 
lone. 
THEOREMA'TICAL, Theorema'tic, or Theore'mic, 
adj. Comprised in theorems; consisting in theorems.— 
Theoremic truth, or that which lies in the conceptions 
we have of things, is negative or positive. Grew. 
THEORE'TICAL, Theore'tic, Theo'rical, or The'- 
ORIC, adj. [theorctique, French; from fteupyT neat;, Gr,; the- 
orique, Fr., from eiexua, Gr.] Speculative; depending on 
theory or speculation; terminating in theory or speculation; 
not practical.—For theoretical learning and sciences there 
is nothing yet complete. Burnet. —The theoretical part of 
the inquiry being interwoven with the historical conjectures' 
the philosophy of colours will be promoted by indisputable 
experiments. Boyle. —Admirably well turned, not only 
for the theoretic, but also the practical behaviour of cun¬ 
ning fellows. Toiler. 
THEORETICALLY, or Theo'rically, adv. Specu¬ 
latively ; not practically.—Able to discourse theorically of 
the dimensions, situation, and motion, of the whole terres¬ 
trial globe. Boyle. 
THEORIA [i^cwpias, Gr.], a solemn annual voyage to 
Apollo’s temple in the island of Delos, performed by the 
Athenians always in the same ship in which Theseus went. 
For the particularities of this naval procession, see Potter's 
Archatol. Grate, lib. ii. 
TIIE'ORIC,Speculation, not practice. 
The bookish thcorick. 
Wherein the toged consuls can propose 
As masterly as he; meer prattle, without practice. 
Is all his soldiership. Shakspcare. 
TIIEORIC MONEY was what was raised, by way of 
tax on the people, to defray the expences of theatrical repre¬ 
sentations, and other spectacles. By a law of Eubulus it was 
made a capital crime to pervert the theoric money to an - 
other use; even to employ it in the occasions of war. 
THE'ORIST, s. A speculatist; one given to specula¬ 
tion.—The greatest theorists have given the preference to 
such a government as that which obtains in this kingdom 
Addison. 
THE'ORY, s. [theoric, Fr.; Secopia, Gr.] Speculation; not 
practice; scheme; plan or system yet subsisting only in the 
mind.—If they had been themselves to execute their own 
theory in this church, they would have seen, being nearer. 
Hooked. 
THEORY, A tomic, in Chemistry, the means of explaining 
the composition and decomposition of chemical bodies, by 
considering their ultimate atoms or particles as peculiar and 
distinct elementary solids, never changing in their figure, 
weight, or volume, under any circumstances. 
It would be difficult to conceive the existence of any com¬ 
pound without supposing it to have originated by union, in 
some way or other, of particles of its elementary constituents; 
but the prevalence of a doctrine, which has been generally 
advanced by mathematicians, viz., the infinite divisibility of 
matter, has never allowed philosophers to conclude that the 
circumstance of compounds being made up of particles, must 
necessarily limit the proportions in which the elements com¬ 
bine. If the elementary bodies be conceived infinitely divi¬ 
sible, the molecules, or compound particles, may be con¬ 
ceived infinitely small, and the number of mean compounds 
existing between any two given extremes may be also con¬ 
sidered infinite. 
If such were the nature of elementary matter, and no other 
causes interfered, there could be no limitation to the pro¬ 
portions in which simple matter would combine. This, 
however, is contrary to fact; as it is a fact known from 
the earliest dawnings of chemical knowledge, that bodies 
are limited in the proportions of their elements; the most 
striking of these facts being the mutual saturation which 
takes place between an acid and an alkali, and the uniform 
proportions afforded in the analysis of many native com¬ 
pounds. 
Philosophers were always satisfied to consider this fact of 
the limitation of the proportions of bodies as one of the 
hidden secrets of nature, as difficult to conceive as the nature 
of the attraction by which their elements were held together. 
Berthollet appea/s to have been the first to attempt this ardu¬ 
ous task, in his ingenious work, entitled “ Chemical Statics.” 
He supposes that the particles of bodies, when brought within 
the sphere of attraction, combine without controul till the 
compound assumes some definite form, by which it is with¬ 
drawn from the situation in which it was formed. He sup¬ 
poses the chemical affinity of bodies to be distinct from that 
power on which their cohesion depends, and also that power 
by which they tend to an elastic state. 
Hence he concludes, that every solid compound is deter¬ 
mined by the cohesion which takes place at some limit in 
the proportion of its elements; such he supposes to be the 
case with salts and other crystallizable compounds. On the 
other hand, he supposes the limitations of the proportions of 
the elements of gaseous compounds to arise from the elastic 
form which they assume in certain stages of combination. 
This hypothesis was supported by so many striking facts, 
that it was thought by some to explain in general the cause 
of limited proportions. All agreed, that whatever might be 
the true theory, the causes pointed out by Berthollet had con¬ 
siderable influence in the composition and decomposition of 
bodies, but they saw at the same time numerous cases in 
which this hypothesis failed to explain the facts. 
Chemists have, from the earliest times, been acquainted 
with those points of limitation which we call mutual satu¬ 
ration, and have been long familiar with those limited aug¬ 
mentations of their proportions, called by some doses and 
by others particles. Among the oxyds of metals, which had 
been little examined before the time of Lavoisier, it was 
found, that instead of having an infinite number of means 
between the lowest and highest stages of oxydation, only a 
certain 
