OPT 
refer to that igre a = the . aii &c. to Cno- 
fracting and refle€ting telefcopes, and micro 
LEscopE and Microscope. Of all the aesean that have 
been made at any time, concerning the nature of light and 
colour, thofe of fir Ifaac Ne wton are pre-eminent, and they 
are comprifed in his «Opt The principal of them 
ere communicated to me ‘Royal Society, feven or eight 
ade, in a letter to the fecretary Mr. 
(oe Co- 
anil under PHospHoRuS, &c 
m them with regard to the materiality of light will be 
rae under Licut, &c. The velocity of light, firft af- 
certained by Roemer, was — ee by Lae 
t and 
h 
Abbé Mazeas, Melville, : . 
Dollond, the - e de Chaulnes, Mr. Lambert, Mr. Can- 
. dela Hire, Dr. Porterfield, Dr. Jurin, Dr. Motte 
Dr. Smith, e . &c.; but our limits 
will not show our particularly eaiwerans them in this 
place; and it is the lefs neceflary to do it, as they occur 
under appropriate articles in various parts of the Cyclo- 
edia. 
= We fhall clofe - article with obferving that we eae - 
enfive work on ee by Dr. Sm 
an elaborate Hit 
oO ° 
relating to Vifion, 
tory of the prefent State of Difcoveries 
optics in every paneled tye af philofaphy ; fo that 
it would be endlefs to enumerate the various writers on this 
ptics likewife arifes perfpeCtive, all the rules 
optics, ca cs, and dioptrics, by the v 
T » for fo it fhould be eee ie ave as 
It owes its birth to painting, 
of it which was employed in 
Vitruvius informs us, that A atharchus, inftruéted by 
fchylus, was the firft who wrote upen t fubje@ ; and 
that atterwards the aay of this art were more dif- 
Agatharchus. w they de{cribed the : heory of this 
e ot inforu weds as their writings have been loft: 
however, the revival of painting in Italy was accompauicd 
with a revival of this art; and the firft perfon who atcempted 
tranfparent table deavo ge 
which rays of light, emitted from them, would make upon 
OPT 
it. The book, which he wrote upon this fubje, is not 
now extant ; and this is the more to be regretted, as it is 
that all the lines, which are eal to one another, and to 
the horizon, if they be inclined to the ground kine, converge 
a pretty complete theory of perfpedtive. 
ments were made in the rules of perfpective by fubfequent 
a aalee ase particularly by profeffor Gravefande, and 
ftill m rook Taylor, whofe principles are, ina ° 
great ae es new, and much more general than thofe of 
any perfon before him, Although Dr. Taylor really in- 
vented his excellent method of perl pective, yet it is fuggetted 
Mr. Robins, that the fame method was publifhed by 
Guido Ubaldi, in his * Perfpe&tive,” oume a Pefaro, in 
1600. In this treatife, the method is delivered very clearly, 
and confirmed by moft excellent demonftrations. In the laft 
book, Ubaldi applies his method to the delineation of - 
fcenes of a theatre ; ae : this, as far as the practice 
concerned, he is followed by fignor Sabatellini, in “his 
se Pra@tica di fabricar Scene,” of which t new 
edition at Ravenna in 16, 8; and to this was added a fecond 
o 
<< 
period for ingenious devices to apply the knowledge they 
had of optics, and nee of per edie. to the purpofes 
of amufement. e ANAMORPHOSIS. 
The principles ie a of per/pective will be illuftrated 
at large under that a 
OPTIMATES, in : Antiquity, one of the divifions of the 
Roman people, o oppofed to populare 
According to - ully’s re Aerie the optimates were the 
beit citizens, or thofe who defired their aGtions might be 
interelt i in ek 
thers aii ‘make the optimates to be the vigorous 
affertors of the dignity of the chief magiftrate, and the 
fticklers for the grandeur of the ftate; who cared not if the 
inferior members uffered, if it were for the advancement 
; and the vopulares, thofe who 
opulace, and encouraged them 
to demand larger ernlere to bring matters nearer to a 
level. 
OPTIO, among the a an affiftant or lieutenant 
belonging to every centurio 
They were called optiones, aaa opto, I choofe 3 ere it 
was in the option of the centurion to choofe whom he pleafed 
for this employment ; though at firtt 1t was alow the 
optio being chofen by the tribune or chief commander of the 
The optiones were not peculiar te the camp, but were 
ufed alfo tu many other offices of life. 
N, the power or faculty a a or choofing 5 
or the choice 2 perfon makes of an 
When a new fuffragan bifhop, Oi. created or ae 
