VIR. 
rants, and especially ripe gooseberries : 
tliese should be mixed in the proportions 
which would give a Strong wine, put into a 
small barrel, which it should fill about three- 
fourths, and the bung-hole very loosely 
stopped. Some yeast, or, what is better, 
a toast sopped in yeast, should be put in, 
and the barrel set in the sun in summer, or 
a little way from a fire in winter, and the 
fermentation will soon begin. I'his should 
be kept up constant, but very moderate, 
till the taste and smell indicate that the 
vinegar is complete. It should be poured 
off Clear, and bottled carefully; and it will 
keep much better if it is boiled for a mi- 
nute, cooled, and strained before bottling. 
Vinegar contains a considerable quantity 
of colouring extractive matter, from which 
it can only be freed by distillation ; the 
process of which will be clearly understood 
by a reference to the article Distil- 
I.ATION. See also Acetic acid. When 
vinegar is long kept, especially exposed 
to the air, it becomes muddy, acquires 
a mouldy, unpleasant smell, loses it^ clear 
red colour and all its properties, and 
finally, is changed to a slimy mucilage and 
water. 
VIOL, in music, a stringed instrument, 
resembling in shape and tone the violin, of 
which it was the origin. 
VIOLA, in botany, violet, a genus of the 
Syngenesiq Monogamia class and order. 
Natural order of Campanacem. Cisti, Jus- 
sieu. Essential character: calyx five-leav- 
ed ; corolla five-petalled, irregular, horned 
at the back ; anthers cohering; capsule 
superior, one-celled, three-valved. There 
are forty three species : some of these plants 
are highly esteemed, particularly the V. 
odorata, sweet violet, for its fragrance ; it 
is a native of every part of' Europe, in 
woods, among bushes, in hedges, and on 
warm banks, flowering early in the spring. 
VIOLIN. See Musical instruments. 
VIOLONCELLO. See Musical instra- 
ments. 
VIPER. See Coluber. 
VIRECTA, in botany, a genus of the 
Pentandria Monogynia class and order. 
Natural order of Rubiace®, Jussieu. Es- 
sential character: calyx five-toothed, with 
teeth interposed ; corolla funnel-form ; stig- 
ma two-parted ; capsule one-celled, many- 
seeded, inferior. There are two species, 
viz. V. biflora, two-flowered virecta; and 
V. pratensis. 
VIRGO, in astronomy, one of the signs 
or constellations of the zodiac, and the 
VIS 
sixth according to order. It is marked 
thus Rg, and in Ptolemy’s catalogue con- 
sists of thirty-two stars, in Tycho’s of thirty- 
nine, and in the Britannic of eighty-nine. 
VIRTUAL/ocms, in optics, is a point in 
the axis of a glass, where the continuation 
of a refracted ray melts it. 
VIS, a Latin word, signifying force or 
power ; adopted by physieal writers to ex- 
press divers kinds of natural powers or 
faculties. Vis impressa is defined, by Sir 
Isaac Newton, to be the action exercised 
on any body, to change its state, either in 
resisting, or moving uniformly in a right 
line. This force consists altogether in the 
action, and has no place in the body, after 
the action is ceased. See Inertia, &c. 
VISCUM, in botany, misseltoe, a genus 
of the Dioecia Tetrandria class and order. 
Natural order of Aggregat®, Linnmus. 
Caprifolia, Jussieu. Essential character : 
male, calyx four-parted ; corolla none; fila- 
ments none ; anthers fastened to the calyx : 
female, calyx four-leaved, superior ; corolla 
none; style none; berry one-seeded; seed 
cordate. There are twelve species. 
VISIBLE, something that is an object 
of sight or vision, or something whereby 
the eye is affected, so as to produce a sen- 
sation. 
The Cartesians say that light alone is the 
proper object of vision. But according to 
Newton, colour alone is filie proper object 
of sight; colour being that property of 
light by which the light itself is visible, and 
by which tlie images of opaque bodies are 
painted on the retina. Philosophers in ge- 
neral had formerly taken for granted, that 
the place to which the eye refers any visi- 
ble object, seen by reflection or refraction, 
is that in which the visual ray meets a per- 
pendicular from the object upon the reflect- 
ing or the refracting plane. That this is 
the case with respect to plane mirrors i^ 
universally acknowledged ; and some ex- 
periments with mirrors of other forms seem 
to favour the same conclusion, and tlius af- 
ford reason for extending the analogy to all 
cases of vision. If a right line be held 
perpendicularly over a convex or concave 
mirror, its image seems to make one line 
with it. The same is the case with a right 
line held perpendicularly within water; for 
the part which is within the water seems to 
be a continuation of that which is without. 
But Dr. Barrow called in question this me- 
thod of judging of the place of an object, 
and so opened a new field of Inquiry and 
debate in this branch of science. This, 
li g 
