BALANINUS. 
whole is suspended when the beam is_hori- 
zontal. 
The perfect equality of the two weights thus 
placed in equilibrio cannot, however, be a mat- 
ter of certainty, unless we know that the two 
arms are exactly equal. In order to determine 
this, we have only to make the weights and the 
body weighed change places; and if the arms are 
unequal, there will no longer be an equilibrium. 
By this means, we only ascertain that the balance 
is imperfect ; but we may, by a very simple pro- 
cess, find the exact weight of any body P by an 
imperfect balance. For this purpose, let us sup- 
pose that the body P, placed in the left hand 
scale, is exactly balanced by the weight W in the 
right hand scale. Take out P, and substitute in 
its place a weight P’, which exactly balances W ; 
then, though, from the known inaccuracy of our 
balance, P is not equal to W, nor P’ equal to W, 
| yet P is equal to the weight P’, because they are 
both in equilibrio with the same weight W, in 
_ the same circumstances.—The Roman steelyard 
is an instrument for finding the weights of dif- 
ferent bodies, by means of a single weight, which 
is placed at a greater or less distance from its 
_ fulcrum, or centre of suspension. It consists of 
_ascale, and sometimes of a hook placed at the 
_ end of the shorter arm for carrying the body to 
| be weighed, and of a weight which is made to 
slide along the longer arm. When the body to be 
weighed is suspended at the end of the shorter 
arm, the constant weight is slipped along the 
long arm, till the equilibrium is indicated by the 
| tongue or index. When this is effected, the num- 
ber at the point at which the weight rests, indi- 
cates the weight of the body. The Danish and 
Swedish steelyard is a lever with a constant 
weight fixed at one extremity, and a scale for 
holding the body to be weighed at the other ex- 
tremity. The point of suspension is therefore va- 
riable, and is generally a ring, which is moveable 
along the lever till an equilibrium takes place. 
In balances where very great accuracy is re- 
quired, the beam is not supported by suspension, 
but has a fine edge of steel for its axis, which 
rests upon steel planes. The horizontal position 
of the beam is in this case determined, by ob- 
serving when the extremities of the arms point to 
the zero of two ivory scales fixed in the maho- 
gany frame in which the instrument is placed, 
the line joining the two zeros having been pre- 
viously placed in a horizontal position, by levels 
fixed in a mahogany frame. The beams of these 
delicate balances sometimes consist of a plain 
cylindrical rod, of a double cone, whose vertices 
form the points of suspension, or of a frame in 
the form of a rhombus. 
BALANINUS. A genus of insects, of the wee- 
vil tribe. One of the species inhabits the acorn ; 
and hence the name balaninus, which is derived 
from a Greek word meaning an acorn, is applied 
to the whole genus. But the species best known 
to cultivators of the soil is Balaninus nucwm, or 
BALL. 
the nut weevil. This species is described as fol- 
lows by Mr. Stephens : — “ Slightly depressed, 
black, densely clothed with flavescent or griseous 
pubescence, with deeper shades and irregular 
fascize ; head furnished with a very long and 
slender rostrum, which is outwardly rufous; tho- 
rax subcarinated; scutellum flavescent or whitish; 
elytra (not covering the extremity of the abdo- 
men), punctate-striated, the interstices thickly 
rugulose; body beneath also pubescent, with the 
pubescence very dense on the anterior angles of 
the breast ; legs dull ferruginous, the joints some- 
what piceous; femora acutely dentate; antennee 
dull ferruginous ; length, from three to five lines.” 
Its form and appearance—as well indeed as those 
of the whole genus—exhibit a close resemblance 
to the genus AnTHoNnomuS; but the proboscis is 
as long as the whole body, very slender, and 
considerably arched. Early in August, when the 
hazel nut is soft and immature, the female of the 
Balaninus nucum, with her long polished beak, 
drills a hole in the nut, and, by means of her 
ovipositor, introduces an egg through the hole ; 
in the course of about a fortnight, the larva is 
hatched, and begins to feed upon the kernel and 
the surrounding pulp; and when full grown, it 
either widens the hole through which the egg 
was deposited, or bores another hole with its 
mandibles, and egresses to bury itself in the 
earth, and there effect its transition through the 
state of a pupa to that of a beetle. The larva is 
short, thick, and fleshy; it lies, when at rest, in 
the form of a semicircle; it has neither hairs nor 
bristles, but is thickly covered with minute tuber- 
cles ; and it does not appear to have either eyes 
or legs. The pupa is of a pale colour; it has two 
projecting points at its hinder extremity; and | 
its head and its rostrum are distinctly formed. | 
Hither Balaninus nucum, or some insect so like | 
it as to have been mistaken for it, has of late | 
years attacked the plants of some English vine- 
ries. It abounds on the continent and in some 
districts of England, but is comparatively rare in 
Scotland. One of the best methods of destroy- 
ing it is, in the end of June or the beginning of 
August, to shake the bushes or beat them with 
a pole, and to collect the insects as they fall 
either in an insect-net held below the bushes, or 
on a sheet spread upon the ground.—/Uustrations 
of British Entomology. — Quarterly Journal of 
Agriculture —Loudon’s Gardener's Magazine. — 
BALK. A piece of arable land left unploughed, 
either through careless management, or by pro- 
digal waste, or with design to serve as a boun- 
dary, or for some other purpose. Balk is also 
the name of the summer-beam or dorman of a 
house; and balks or bawks are poles laid over a 
stable or other building for a roof. 
BALL, Any thing rotund or globular. But 
the word is technically used in farriery to desig- 
nate a cylindrical or egg-shaped mass of medi- 
cine, tightly skinned with paper, and adminis- 
tered as a dose to a horse. A ball, in this techni- 
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