Dec. 1, 1899.] Supplement to the Tropical Agriculturist.''' 43^ 
circulation. It often happens that vegetable matter 
remains for a long time in the form of humus ; but 
even in this form it is utilised by plants. The humus 
is constantly subjected to the oxidising action of 
the lower organisms, and undergoes gradual 
decomposition. The ammonia produced by the 
dt'compositiou of the humus is assimilated by 
plants as well as the readily available product of 
oxidation, nitric acid. Schloesing and Miintz 20 
years ago showed that nitrates are formed in the 
soil by the action of organisms. More recently 
Winogradsky has demonstrated that the action of 
two different organisms is necessary for the trans- 
formation of ammonia into nitrates ; one converts 
ammonia into nitrites and the other completes the 
oxidation, producing nitrates. We thus see that 
micro-organisms seize upon the nitrogen of the 
air and convert it into organic compounds; they 
convert vegetable matter into hu mus, and then 
breaks down this humus, producing ammonia and 
finally nitrates. At every step they perform a 
useful work, and are valuable auxiliaries of agri- 
culture. There are, however, other organisms 
which interfere with the work of beneficial kinds. 
Br6al observed several years ago that there is an 
aerobic organism which decomposes nitrates and 
sets elementary nitrogen free. This organism is 
abundant in vegetable d6bris, especially in straw. 
It is also encountered in the excrement of domestic 
animals. The extent to which the losses of nitro- 
gen in arable soils is due to the action of this 
dentrifying organism and the conditions most 
favourable to its action are questions which 
require further investigation. 

NOTES ON EXHIBITS FOR PARIS. 
Edible Bibds' Nests. 
(Continued.) 
Portman is quoted by Dr. Watl as having 
published an intere-ting account of collecting 
the nests as pursued in the Andaman Islands: — 
"Before the arrival of the swallows, and as soon 
as the weather is sufficiently settled, say, about 
the first week in November, all the caves in the 
islands should be visited and thoroughly cleaned, 
tlie portions of old nests and debris being removed. 
After the arrival of the birds, and as soon as it is 
ascertained ihat they have built their nests, all 
the caves should be visited and the nests collected 
and brought in. The date of this visit, and, 
indeed, the number of collections, during the 
seasons are fixed by the time at which the north- 
east monsoon rain ceases. Being unusually late 
this year (1885-86), we did not commence nest- 
collecting till the end of Pebruary, but with a 
dry December the collection might commence on 
the loth January. As the collection of nests 
from the present known caves takes about a 
month, and the swallows rebuild their nest in six 
weeks or so, the collectors should wait about ten 
days in Port Blair, and then go out again, taking 
care to observe exactly the same order in their 
rounds. The nests may be collected until the 
commencement of. the rains, when the collection 
should cease, and the birds be left to breed. 
Although the great demand is for the white 
nests, still it may be remarked that the fucus 
attachments of the grass nests, aud the old nests 
gathered in November cleaning, may be sold 
locally at Eo per seer, and should, therefore, be 
collected. Each collection averages about 52 lb. 
of nests." He then proceeds to state the number 
of men employed by Government to collect the 
uests, addiug : " The six collectors are supplied 
with torches, rough ladders, axes, and dahs, also 
with a large clean bag lined with linen slung to 
the side, and an iron implement, about a foot 
long, with three prongs at one head, and the 
other end being shaped like a cold chisel. These 
men detach, with this implement, nests from the 
aides and roofs of the caves, placing them care- 
fully in their bag, from which, at the end of 
the work, they are transferred to a box provided 
with a lock." 
In cooking the nests, they are first soaked in 
cold water for two hours, when they swell up 
and become soft. They are then easily picked to 
pieces and cleaned. After this they are boiled in 
clear chicken-brotli until dissolved, a process 
occupying about two hours longer. The usual 
allowance is one nest (value Rl) to a tea-cup of 
soup. Any clear soup may be used. The nest 
is tibsnlutely tasteless and flavourless, but Mr. 
Portman does not consider them to be particularly 
strengthening or useful in any way. 
Particulars are not available regarding the full 
extent of the Indian trade in nests. The 
merchants are Chinamen who reside in Rangoon. 
They recognise three classes :— 
No. 1. Large,purewhitenests averaging from 
RlIO to R115 per viss = 3^ lbs. 
No. 2. Clean but slightly coloured nests, aver- 
aging from RlOO to RI40 a viss. 
No. 3. More discoloured and dirty nests. 
The refuse sells at from Eo to R15 a seer. 
Balfour states that 8| million nests are annually 
imported into Canton, and that nests of the first 
quality fetch from £5 to £6 the lb. ; those of the 
second, 9s. 4^d, ; those of the third, 3s. Id. 
McCulloch says that the second quality fetches 
£4 14s., and the third £2 15s. The bulk of the 
more expensive nests are sent to Pekin for the 
use of the Court. The Japanese do not use the 
nests, but they prepare from a sea-weed an 
artificial nest called Dschin-Schan, which they 
export to China. Of the Eatnagiri District it is 
stated the right to collect nests is farmed out to 
Goanese. The Andaman contractor used to pay 
E3,000, but last year, owing to the contractor 
having thrown up his contract, the Government 
worked the nesting and realized £4,900. 
In Ceylon Collocalia nidifera is widely distri- 
buted with the exception of the North and North- 
western Provinces. It does not confine itself to 
any one altitude, even its building station ex- 
tending from the seaside to the highest hills. 
These swifts select for their breeding places large 
dark and gloomy caverns, in the darkest parts of 
which they build their famous nests. These may 
number only a few or thousands, and are not 
always made of the same substances. The Ceylon 
nests are considered to be very poor in nutritive 
properties in comparison with those of Javo, 
Borneo and China, having much less glutinous 
matter in their composition. The nests are 
closely built together against the face of some 
overhanging rock, aud if one may judge by the 
