B A R 
B A R 
BAR 
203 
Bark-bed, in gardening, that sort of hot- 
bed, which is wholly or ' principally consti- 
tuted of tanner’s bark, commonly employed 
in a hot-house, because it retains its heat 
loi oer and emits less steam than a hot-bed 
of horse-dung. 
Bark-bound, a disease in trees thought 
to be capable of being cured by making a 
slit or opening through the bark. 
Bark-longue, or Barca Longa, a small 
low sharp-built but very long vessel, without 
2 deck. It goes with sails and oars, and is 
very common in Spain. 
BA11LERIA, a genus of the angiospermia 
order, and didynamia class of plants ; and in 
the natural method ranking under the 40th 
order, personate. The calyx is quadripar- 
tite; two of the stamina are much less than 
the rest ; the capsule is quadrangular, bilo- 
cular, bivalved, elastic, and without claws ; 
and the seeds are two. There are eleven 
species ; all natives of the warm parts of 
America, and therefore require to be kept 
in a stove, and treated like other tender 
exotics. They possess no great beauty nor 
any remarkable property ; but are kept for 
the sake of variety. 
BARLEY. See Hordeum. 
Barley-corn, the least of our long-mea- 
sures, being the third of an inch. 
Barley, pearl, and French Barley, are 
barley freed from the husk, and rounded 
by a' mill ; the distinction between the 
two being that the pearl barley is reduced to 
the size of small shot, all but the heart being 
ground away. 
i BARM. See Yeast. 
BARN ABIT ES, a religious order, founded 
in the sixteenth century, by three Italian 
gentlemen, who had been advised by a famous 
preacher of those days to read carefully the 
epistles of St. Paul. Hence they were call- 
ed clerks of St. Paul, and Barnabites, because 
they performed their first exercise in a church 
of St. Barnabas at Milan. Their habit is 
black, and their oliice is to instruct, cate- 
chise, and serve in mission. 
BARNACLE, or Bernicle, in ornitho- 
logy. See Anas. 
Barnacles, in farriery, an instrument 
composed of two branches joined at one end 
with a hinge, to put upon horses’ noses when 
they will not stand quietly to be shod, 
blooded, or dressed. 
BARNADESIA, in botany; a genus of 
the polygamia squabs order, and syngenesia 
class of plants; the characters of which are : 
the corolla is radiated ; the calyx is naked, 
imbricated, and pungent ; the pappus of the 
rays feathery, of the disk bristly and retro- 
fracted. There is but one species, viz. 
Barnadesia Spinosa, a native of South Ame- 
rica. 
BAROCO, in logic, a term given to the 
fourth mode of the second figure of syllo- 
gisms. A syllogism in baroco has the first 
proposition universal and affirmative, but the 
second and third particular and negative, 
and the middle term is the predicate in the 
two first propositions. For example : 
Every virtue is attended with discretion : 
Some kinds of zeal are not attended with 
discretion ; 
Therefore some kinds of zeal are not vir- 
tues. 
BAROMETER, a machine for measuring 
the weight of the atmosphere. The baro- 
meter is founded on an experiment of Torri- 
celli, who considering that a column of water 
of about thirty-three feet was equal in weight 
to a column of air of the same base, conclud- 
ed that a column of mercury, no longer than 
about twenty-nine inches and a halt, would 
be so too, such a column of mercury being 
as heavy as thirty-three feet of water. Ac- 
cordingly he tried the experiment, and the 
apparatus he made use of is now the com- 
mon barometer or weather-glass. 
The tubes of which barometers are made 
ought to be at least one fourth of an inch 
bore ; but one third or even one half of an 
inch is better. The tube should be new, and 
perfectly clean within. In order to this, it 
should be hermetically sealed at both ends, 
at the glass-house, when made; one ot the 
ends may be cut off with a tile, w hen you 
use it. The mercury ought to be perfectly 
pure, and should be purged from air by boil- 
ing it in a tube. 
To fill the tube with mercury, warm it, 
and pour some mercury into it by a small 
paper funnel, so as to reach within an inch 
of the top ; you will see that as the tube fills, 
there are bubbles of air in several parts. 
When the tube is full, apply your finger hard 
against the open end, and invert it; by which 
means the air that was on the top, now ris- 
ing through all the quicksilver, gathers every 
bubble in its way. Turn the tube up again, 
and the bubble of air re-ascends ; and, if 
there are many small bubbles left, carries 
them away. If, however, any remain, the 
operation must be repeated. The tube is 
now to be tilled to the top, and stopping the 
open end with the finger, must be inverted 
into a bason of mercury. When the end of 
the tube is perfectly plunged under the sur- 
face of the mercury, the finger must be 
taken away, and the mercury in the tube will 
subside, remaining suspended at the height 
of 29 or 30 inches, according to the pressure 
of the atmosphere at the time. The space 
at the top of the lube is a perfect vacuum. 
The following is a still better way of filling 
the tube: Pour the purest mercury into the 
tube (which must be very dry and well clean- 
ed), to within two inches of the top, and 
then hold it with the sealed end lowest, in an 
inclined position, over a chafing-dish of burn- 
ing charcoal, placed near the edge of a table, 
in order that all parts of the tube may be 
exposed successively to the action of the fire, 
by moving it obliquely over the chafing-dish. 
The sealed end is to be first gradually pre- 
sented to the fire. As soon as the mercury 
becomes hot, the internal surface of the tube 
will be studded with an infinite number of 
air-bubbles, giving the mercury a kind of 
grey colour : these increase in size by run- 
ning into one another, and ascend towards 
the higher parts of the tube, where, meeting 
with a cooler part of the fluid, they are con- 
densed, and nearly disappear. In conse- 
quence, however, of successive emigrations 
towards the upper parts of the tube, which 
are successively heated, they finally acquire 
a bulk, which enables them in their united 
form entirely to escape. When the first 
part of the tube is sufficiently boiled, move 
it onward, by little and little, through its 
whole length. When the mercury boils, its 
parts strike against each other, and against 
the sides of the tube, with such violence, 
C c 2 
that a person unacquainted with the ope- 
ration, naturally apprehends the destruction 
of his tube. By this process the mercury 
is entirely deprived of the air which adhered 
to it. 
The tube is now fixed with its bason to a 
wooden frame prepared for it, having a scale 
of inches at the upper end, which is accu- 
rately measured from the surface of the mer- 
cury in the cistern. (Plate IX. Miscel. fig. 6.) 
Fig^ 7 shews the scale or vernier at the top, 
drawn larger. 
This is the common construction of the 
barometer, and is still found to be the best. 
However, as the space through which the 
upper part of the mercury in the tube has 
to rise and fall does not exceed three 
inches, from 28 inches to 31 above the mer- 
cury in the bason, several contrivances have 
been used to increase the scale, and thereby 
shew more sensibly small changes; the 
chief of which are the following : 
The diagonal barometer. ABC (fig. 8) 
is a tube sealed at C, immersed in mercury 
at A ; this tube is perpendicular from A to 
B, where the scale of variation begins; thence 
it is bent into B C. This part B C proceeds 
to the highest limit in the scale of variation, 
viz. I C ; and consequently, while the mer- 
cury rises from I to C in the common ba- 
rometer, it will move in this from B to C ; 
and so the scale will be by this means en- 
larged in the proportion of B C to I C. 
This form however, being subject to a great 
degree of friction, on account of the ob- 
liquity in the part B C, which inclination 
makes the quicksilver frequently divide into 
several parts, it requires the trouble of filling 
tubes anew too often. 
The horizontal, or rectangular barometer, 
consists of a tube A C I) F (fig. 9), sen led 
on the upper end A, and bent to a right angle 
at D. 1 he mercury stands in both legs from 
Eto C, Here it is evident, that in moving 
three inches from Ato C, it will move through 
so many times three inches in the small leg 
D F, as" the bore of D F is less than the bore 
of A C, whence the motion of the mercury 
at E must be extremely sensible, This form 
is liable to the same exceptions as remarked 
in that of fig. 8; and, besides a great degree 
of friction, and the frequent breaking olf of 
the mercury in the leg E, the part D F being 
a very small bore, the free motion of the 
mercury must be impeded by the attraction 
of cohesion. 
The zvheel barometer. A (fig. 10), repre- 
sents the quicksilver in a glass tube, having 
a large round head or ball, and tumedup at 
bottom B; upon the surface of the mercury 
in the recurved leg, there is then placed a 
short glass tube loaded with mercury, with 
a string going over a pulley, and is balanced 
by another weight hanging freely in the air. 
As the surface at A is very large/ and that at 
B very small, the motion of the quicksilver 
and consequently of the ball, will at the bot- 
tom be very considerable ; but as the weight 
moves up and down, it turns the pulley, and 
that a hand or index ; and by tiie divisions 
of a large graduated circle, the minutest vari- 
ations of the air are plainly shewn, if the in- 
strument is accurately made, and the friction 
of the several parts inconsiderable. 
There is also a barometer, contrived so as 
not to be affected by the motion of a ship, 
called the marine barometer. 
