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not melt when heated ; and when treated 
with nitric acid, it neither becomes yellow, 
nor does it yield resin. Acetic acid softens 
bird-lime, and dissolves a certain portion of 
it. The liquid acquires a yellow colour. Its 
taste is insipid. When carbonate of po tash 
is dropped into this solution, no precipitate 
falls. By evaporation it yields a resinous- 
like substance. Some of the metallic oxides 
are reduced when heated with bird-lime. 
Litharge combines with it, and forms a 
kind of plaster. Alcohol of the specific 
gravity 0.817 dissolves bird-lime at a boiling 
heat. On cooling, it lets fall a yellow mat- 
ter similar to wax. The filtered liquid is 
bitter, nauseous, and acid. Water precipi- 
tates a substance similar to resin. Sulphu- 
ric ether dissolves bird-lime readily, and 
in great abundance. The solution is green- 
ish. When mixed with water, an oily sub- 
stance separates, which has some resem- 
blance to linseed oil. When evaporated, a 
greasy substance is obtained, naving a yel- 
low colour and the softness of wax. 
Birds’ nests, in cookery, the nest of a 
small Indian swallow, very delicately tasted, 
and frequently mixed among soups. On 
the sea coasts of China, at certain seasons 
of the year, there are seen vast numbers of 
these birds ; they leave the inland-country 
at their breeding time, and come to build 
in the rocks, and fashion their nests out of a 
matter which they find on the shore, 
washed thither by the waves. The nature 
of this substance is scarcely yet ascertained. 
According to Kempfer, it is molluscas 01 
sea-worms ; according to M. le Poivre, 
fish-spawn; according to Dalrymple, sea- 
weeds ; and according to Linnaeus, it is the 
animal substance frequently found on the 
beach, which fishermen call blubbers or 
jellies. The nests are of a hemispheric fi- 
gure, and of the size of a goose’s egg, and 
in substance much resemble the ichthyo- 
colla or isinglass. The Chinese gather 
these nests, and sell them to all parts of the 
world; they dissolve in broths, &c. and make 
a kind of jelly of a very delicious flavour. 
These nests are found in great abundance 
in the island of Sumatra, particularly about 
Croe, near the south end of the island. Four 
miles up the river of that name is a large 
cave, where the birds build in vast num- 
bers. The nests are distinguished into white 
and black ; of which the first are by far 
more scarce and valuable, being found in 
the proportion of one only to twenty-five. 
The white sort sells in China at the rate of 
1000 to 1500 Spanish dollars the pecul ; 
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the black is usually disposed of at Batavia 
for about 20 dollars the same weight, where 
it is chiefly converted into glue, of which it 
makes a very superior kind. The diffe- 
rence between the two has by some been 
supposed to be owing t <i the mixture of the 
feathers of the birds with the viscous sub- 
stance of which the nests are formed ; and 
this they deduce from the experiment of 
steeping the black nests for a short time in 
hot water, when they are said to become in 
a great degree white. When the natives 
prepare to take the nests, they enter the 
caves with torches, and forming ladders ac- 
cording to the usual mode, of a single bam- 
boo notched, they ascend and pull down the 
nests, which adhere in numbers togetliei, 
from the side and top of the rocks. ’ hey 
say that the more frequently and regularly 
the cave is stripped, the greater proportion 
of white nests they are sure to find, and 
that on this experience they often make a 
practice of beating down and destroying 
the old nests in larger quantities than they 
trouble themselves to carry away, in order 
that they may find white nests the next sea- 
son in their room. The birds, during the 
building time, are seen in large flocks on 
the beach, collecting in their bills the foam 
which is thrown up by the suif, of which 
there is little doubt but they construct their 
nests, after it has undergone perhaps a pre- 
paration, from a commixture with their sa- 
liva, or other secretion with which nature 
has provided them for that purpose. 
Birds, singing, are, the nightingale, 
blackbird, starling, thrush, linnet, lark, 
throstle, canary-bird, bulfinch, goldfinch, & c. 
See some very curious experiments and ob- 
servations on the singing of birds, Phil. 
Trans, vol. lxiii. part ii. No. 31. Their 
first sound is called chirp, which is a single 
sound repeated at short intervals ; the next 
call which is a repetition of one and the 
same note ; and the third sound is called re- 
cording, which a young bird continues to do 
for ten or eleven months, till he is able to 
execute every part of his song ; and when 
he is perfect in his lesson, he is said to sing 
his song round. Their notes are no more 
innate than language in man ; they all sing 
in the same key. The honourable author, 
Daines Barrington, has attempted to re- 
duce their comparative merits to a scale ; 
and to explain how they first came to have 
particular notes. 
Birds, in heraldry, according to their se- 
veral kinds, represent either the contem- 
plative or active life. They are the ern- 
