UND 
pendent ones can add notliing, but must 
weaken a little ; and after a point is well 
settled by a number of independent ones, 
all that come afterwards are in one sense 
useless, because they do no more than re- 
move the imperceptible remaining defici- 
ency ; on the other hand, however, as evi- 
dence produces different effects on differ- 
ent minds, it is of great moment in all points 
of general importance, to have as many 
satisfactory independent evidences as possi- 
ble brought into view ; that if one feii in 
its effects, from peculiar circumstances, 
another may supply its place. And it will 
be of great use to pursue these and such 
like deductions, botlr mathematically, and 
by applying them to proper instances se- 
lected from the sciences, and from common 
life, in order to remove certain prejudices, 
which the use of general terms and ways of 
speaking, with the various associations with 
them, is apt to introduce and fix upon the 
mind. It cannot but assist ns, in the art 
of reasoning, thus to analyse, recompose, 
and ascertain our evidences. 
UNDULATION, in physics, a kind of 
tremulous motion or vibration observable 
in a liquid, whereby it alternately rises and 
falls like the waves of the sea. Thus undu- 
latory motion, if the liquid be smooth and 
at rest, is propagated in concentric circles, 
as most people have observed upon throw- 
ing a stone, or other matter, upon the sur- 
face of a stagnant water, or even upon 
touching the surface of the water lightly 
with the finger, or the like. The reason of 
these circular undulations is, that by touch- 
ing the surface with your finger, there is 
produced a depression of the water in the 
place of contact. By this depression, the 
subjacent parts are moved successively out 
of their place, and the other adjacent parte 
thrust upwards, which lying successively on 
the descending liquid, follow it j and thus 
the parts of the liquid are alternately raised 
and depressed, and that circularly. When 
a stone is thrown into the liquid, the reci- 
procal vibrations are more conspicuous : 
here the water, in the place of immersion, 
rising higher by means of the impulse, or 
rebound, till it comes to fall again, gives an 
impulse to the adjoining liquid, by which 
means that is likewise raised about the 
place of the. stone as about a centre, and 
forms the first undulous circle ; this falling 
gives another impulse to the fluid 
next to it, further from the centre, which 
rises likewise in a circle : and thus succtes- 
VOL. VI, 
UNI 
sively greater and greater circles are pro- 
duced. 
UNGULA, in geometry, the section of a 
cylinder cut off by a plane passing obliquely 
through the plane of the base and part of the 
cylindric surface. 
UNICORN, an animal famous among 
the ancients, but looked upon by the mo- 
derns as fabulous, denominated from its dis- 
tinguishing characteristic of having one horn 
only, which is represented as five palms 
long, and growing in the middle of the fore- 
head. 
The unicorn is one of the supporters of 
the British arms. It i^ represented, by 
heralds, passant, and sometimes rampant. 
When in this last action, as in the British 
arms, it is properly said to be saillant. Ar- 
gent, an unicorn sejant sable, armed and 
unguled, or, borne by the name of harding. 
Unicorn/sA. See Monodon. 
UNIOLA, in botany, a genus of the Tri- 
andria Digynia class and order. Natural 
order of Gramina. Graminem, Jussieu. 
Essential character: calyx many-valved: 
spikelet ovate, keeled. There are three 
species. 
UNONA, in botany, a genus of the Po- 
liandiia Polygynia class and order. Natural 
order of Coadunatae. Anonae, Jussieu. Es- 
sential character : calyx three-leaved; petals 
six ; berries two or three-seeded, jointed like 
a necklace. There are four species. 
UNISON, in music, the effect of two 
sounds which are equal in degree of tune 
or in point of gravity and acuteness. ’ 
UNITARIANS, in church history, are 
those who believe that there is but one 
God, the supreme object of religious wor- 
ship ; and that this God is the Father only, 
and not a Trinity consisting of Father’ 
Son, and Holy Ghost. ’ 
The Unitarians having been frequently 
confounded with the old Socinians, it is 
but justice to observe, that a very material 
difference exists in some parts of the reli- 
gious faith of these two sects. The Soci- 
nians believed that Jesus Christ, though a 
human being, was advanced by God to the 
government of the whole created universe 
and was, tlierefore, the proper object of re- 
ligious worship. On account of their essen- 
tial deviation from the doctrine of Socinus, 
in this and some other respects, the modern 
Unitarians disclaim the appellation Socinian 
as inapplicable to their views of religious faith 
and worship. This term is, however, very 
comprehensive, and is applicable to a great 
