VIT 
scquently, when such objects are brought 
nearer than six inches, tliey will become 
less distinct ; and if to four or three, they 
will scarce be seen at all. But by the help 
of convex glasses we are enabled to view 
things clearly at much shorter distances 
than these ; for the nature of a convex lens 
is to render an object distinctly visible to 
the eye at the distance of its focus ; where- 
fore the smaller a lens is, and the more its 
convexity, the nearer is its focus, and the 
more its magnifying power. Now, it is 
evident from the figure, that if either the 
cornea, or crystalline humour, or both of 
them, be too flat, their focus will not be on 
the retina, where it ought to be, in order 
to render vision distinct, but beyond the 
eye. Consequently those rays which flow 
from the object, and pass through the hu- 
mours of the eye, are not sufficiently con- 
verged to unite, and therefore the observer 
can have but a very indistinct view of the 
object. This is remedied by placing a con- 
vex glass, of a proper focus, befoi'e the eye, 
which makes the rays converge sooner, and 
imprints the image duly on the retina. If 
either the cornea or crystalline humour, or 
both of them, be too convex, the rays that 
enter in from the object will be converged 
to a focus in the vitreous humour, and by 
diverging from thence to the retina, will 
form a very confused image thereon, and 
so of course, the observer will have as con- 
fused a view of the object, as if his eye had 
been too flat. This inconvenience is reme- 
died by placing a concave glass before the 
eye, which glass, by causing the rays to di- 
verge between it and the eye, lengthens 
the focal distance, so that if the glass be 
properly chosen, the rays will unite at the 
retina, and form a distinct picture of the 
object upon it, 
VISMEA, in botany, a genus of the Do- 
decandria Trigynia class and order. Natural 
order of Onagrse, Jussieu; Essential cha- 
racter: calyx five-leaved, inferior j corolla 
five-petalled ; stigmas five ; nut two or 
three- celled, half inferior. There is but one 
species, viz. V. mocanera, a native of the 
Canary islands. 
VISUAL, in general, something belong- 
ing to vision. Thus, rays of light, coming 
from an object to the eye, are called visual 
l ays ; and the visual point in perspective is 
a point in the horizontal line, wherein all 
the visual rays unite. 
VITAL air. See Oxygen gas. 
VITEX, in botany, chaste-trec, a genus 
of the Didynamia Angiospeiinia class and 
VIT 
order. Natural order of Personatae. Vitices, 
Jussieu. Essential character: calyx five- 
toothed; corolla- border six-cleft; drupe 
one-seeded; a four-celled nut. There are 
fourteen species. 
VITIS, in botany, the vine, a genus of 
the Pentandria Monogynia class and order. 
Natural order of Hederaceae. Vitices, Jus- 
sieu. Essential character : petals cohering 
at the top, shrivelling; berry five-seeded, 
superior. There are twelve species, and 
many varieties. 
The most important species of the vitis 
is V. vinifera, or common vine, w'hich has 
naked, lobed, sinnated leaves. There are 
a great many varieties ; and all the sorts 
are propagated either from layers, or cut- 
tings ; ' tlie latter method is said to be pre- 
ferable, though the former is much used in 
this country. 
The uses of the fruit of the vine for mak- 
ing wine, &c.-are well known. The vine 
was introduced by the Romans into Bri- 
tain, and appears formerly to have been 
very common. From the name of vine- 
yard yet adhering to the ruinous scites of 
our castles and monasteries, there seem to 
have been few in the country but what had 
a vineyard belonging to them. The county 
of Gloucester is particularly commended by 
Malmsbury, in the twelfth century, as ex- 
celling all the rest of the kingdom in the 
number and goodness of its vineyards. In 
the earlier pefiods of our history, the isle of 
Ely was expressly denominated the isle of 
Vines by the Normans. Vineyards are fre- 
quently noticed in the descriptive accounts 
of Doomsday ; and those of England are 
even mentioned by Bede, as early as the 
commencement of the eighth century. 
, Doomsday exhibits to us a particular 
proof that wine was made in England du- 
ring the period preceding the conquest; 
and after the conquest, the bishop of Ely 
appears to have received at least three or 
four tons of wine annually as tithes, from 
the produce of the vineyards in his diocese, 
and to have made frequent reservations in 
his leases of a certain quantity of wine for 
rent. A plot of land in London, which now 
forms East Smitlitield and some adjoining 
streets, was withheld fiom the religions 
house within Aldgate by four successive 
constables of the tower, in the reigns of 
Rufus, Henry, and Stephen, and made by 
them into a vineyard, which yielded great 
emolument. In the old accounts of rectorial 
and vicarial revenues, and in the old regis- 
ters of ecclesiastical sails caacerning them, 
