BIR 
predecessors. This prospect gives us a kind 
of security for the continual propagation 
and extension of knowledge ; and that, for 
the future, no more great chasms of men 
really eminent for knowledge will ever dis- 
figure that part of the chart of their lives 
which I cannot draw, or ever see drawn. 
What a figure must science make, advanc- 
ing as it now does, at the end of as many 
centuries as have elapsed since the Augus- 
tan age !” 
BIPED, in zoology, an animal furnished 
with only two legs. Men and birds are 
bipeds. Apes occasionally walk on their 
hind legs, and seem to be of this tribe ; but 
that is not a natural position for them, and 
they rest upon all their legs, like other qua- 
drupeds. The jerboas are also of the latter 
description, jumping and leaping on their 
hind legs, but resting on the fore legs like- 
wise. 
BIQUADRATIC power, in algebra, the 
fourth power or squared square of a num- 
ber, as 16 is the biquadratic power of 2 ; 
for 2 x 2 is 4, and 4 X 4 is equal to 16. 
Biquadratic root of a number, is the 
square root of its square root : thus the bi- 
quadratic root of 81 is 3 ; fou the square root 
of 81 is 9, and the square root of 9 is 3. 
Biquadratic equation, an equation where 
the unknown quantity of one of the terms 
has four dimensions. 
Any biquadratic equation may be con- 
ceived as generated by the multiplication of 
four simple equations. Thus, if x — a, 
x — b,x = c,x — d, or r — a = 0, x — 
6 = 0, x — c = 0, x — d — 0 ; then will 
x — a X x — b X x — ex* — d = 0, be- 
get a biquadratic equation. Or it may be 
formed of two quadratic equations, as 
-f c x x 2 -(- d x e = 0 ; or, last- 
ly, it may be produced from the multiplica- 
tion of one cubic and one simple equation, 
as x — a X x i -{-cx i -j-dx-\-e = 0. For 
an account of the resolution of biqua- 
dratic equations see Equations. __ 
BIQUINTILE, an aspect of the planets, 
when they are 144 degrees from each other. 
BIRCH tree. See Betula. 
BIR D, in zoology- See Aves. 
BiRD-caic/tiKg, the art of taking birds or 
wild fowl, whether for food, for the plea- 
sure of their song, or for their destruction, 
as pernicious to the husbandman, &c. The 
methods are by bird lime, nets, decoys, &c. In 
the suburbs of London are several weavers 
and other tradesmen, who, during the 
months of October and March, get their 
BIR 
livelihood by an ingenious, and, we may 
say, a scientific method of bird-catching, 
which is totally unknown in other parts of 
Great Britain. The reason of this trade be- 
ing confined to so small a compass arises 
from there being no considerable sale of 
singing birds, except in the metropolis : as 
the apparatus for this purpose is also heavy, 
and at the same time must be carried on a 
man’s back, it prevents the bird-catchers 
going to more than three or four miles dis- 
tance. 
This method of bird-catching must have 
been long practised, as it is brought to a 
most systematical perfection, and is attend- 
ed with a very considerable expense. The 
nets are a most ingenious piece of mecha- 
nism ; they are generally twelve yards and a 
half long, and two yards and a half wide ; 
and no one, on bare inspection, would ima- 
gine, that a bird, who is so very quick in all 
its motions, could be catched by the nets 
flapping over each other, till he becomes an 
eye-witness of the pullers seldom failing. 
The wild birds fly, as the bird-catchers 
term it, chiefly during the month of Octo- 
ber, and part of September and November, 
as the flight in March is much less consi- 
derable than that of Michaelmas. It is to 
be noted also, that the several species of 
birds of flight do not make their appearance 
precisely at the same time, during the 
months of September, October, and No- 
vember. The pippet, a small species of 
lark, for example, begins to fly about Mi- 
chaelmas ; and then the woodlark, linnet, 
goldfinch, chaffinch, greenfinch, and other 
birds of flights succeed, all of which are not 
easily to be caught, or in any numbers at 
any other time, and more particularly the 
pippet and the woodlark. These birds, 
during the Michaelmas and March flights, 
are chiefly on the wing from day-break to 
noon, though there is afterwards a small 
flight from two till night; but this how- 
ever is so inconsiderable, that the bird- 
catchers always take up their nets at noon. 
The bird-catcher generally carries with him 
five or six linnets, of which more are caught 
than any singing bird, two goldfinches, two 
greenfinches, one woodlark, one redpoll, 
yellowhammer, titlark, and aberdevine, 
and perhaps a bullfinch ; these are placed 
at small distances from the nets, in little 
cages. He has besides what are called flur- 
birds, which are placed within the nets, are 
raised upon the flur, or moveable perch, 
and gently let down at the time the wild 
bird approaches them. These generally 
M m 2 
