564 
NATURE 
[ April 13, 1882 
the food remaining in the alimentary canal, first of all in 
a more or less solid form and of a dark colour, but after 
it has become fully enveloped in the cocoon the excrement 
comes away as a light-coloured liquid, the hue and con- 
sistency of which depend upon the amount of vegetable 
matter not previously evacuated and the amount of lime, 
carbon, and ammonia present. The respective propor- 
tions of these ingredients vary, I presume, with the food 
upon which the caterpillar has fed, and with the state of 
the atmosphere at the time of spinning ; also the longer 
they remain coating the fibre the harsher and more dis- 
coloured it will be. It is therefore very necessary, I 
think, to remove this cement at a very early date; and 
this chemistry has shown the manufacturers how to do. 
Judicious feeding too may alter its nature. Before long, 
fresh cocoons will be at an early stage thoroughly cleansed 
from all discolouring matter, and Tasar silk will be avail- 
able for manufacturing purposes as colourless as it is 
when first put forth by the caterpillar” (p. 21). 
At any rate here is a fine field for both economic 
and philosophical results for both the chemist and the 
naturalist. 
There are two crops of Tusser silk in the year, z.e. two 
generations of grubs pass from the egg to the imago, 
whereas the Bombyx of commerce so passes only once. 
The moth is considered a sacred insect, and it is interest- 
ing to read of the long series of ascetic ordinances con- 
nected with the attendance upon it, the failure to observe 
which will bring down the anger of the gods and destruc- 
tion upon the cultivators. Yet the grubs are said to 
flourish better out-of-dceors than under the roof and care 
of men, and are found feeding upon seventeen different 
species of trees growing wild over various parts of Hin- 
dostan. It is much more practicable and hopeful to 
engage the unenterprising natives in its collection under 
these conditions than if the elaborate art with which the 
Chinese cultivate the Bombyx were required. 
The silk of the Eria and Moonga or Muga cocoons is 
softer and of a clearer colour than the Tusser silk, but 
lacks the strength of that very coarse variety. It dyes 
well, but is difficult to wind. In all respects therefore it 
is easier to work it up into spun silk. 
The favourite food of the Eria is the Palma Christz or 
castor oil plant, ARzcznzs communis. So productive is this 
worm that it sometimes gives twelve broods, z.e. genera- 
tions, in a year. 
The Muga worm breeds five times ; the colour of the 
silk varies with the food, some of it retaining its drabby 
colour till the last. The moths of all these genera are 
large and handsome. The magnificent A¢facws atlas 
moth, called in France Le Géant des Papillons, measures 
upwards of ten inches in expanse of wing. Itisacommon 
idea that moths ea? their way out of their cocoons, and 
that all permitted to do so spoil their silk; but even in 
the case of the solid cocoon of the Tusser moth it is ob- 
served that ‘‘ after eight or nine months in the pupa state 
a moist spot is observed at one end of the cocoon. The 
moth is now about to emerge both from its pupa shell 
and from the cocoon. It secretes an acid fluid which 
softens the cement of the cocoon, and enables it to sepa- 
rate the fibres sufficiently to allow of its creeping out” 
(p. 19). Capt. Brooke also says that “in Seonee the 
pierced cocoons are wound, and that no koshtee rejects a 
cocoon simply because the moth has eaten its way through 
it. ... It does not eat its way out but separates the 
fibres with its legs and wing-spine, and so creeps out. It 
has neither teeth nor mouth proper” (p. 26). More re- 
markable still is the provision made by the larva of this 
Attacus atlas, “the upper extremity of whose cocoon 
forms a natural orifice for the exit of the moth, made by 
the conveyance of a great number of silk fibres which are 
left ungummed, and are thus soft and flossy ; thus the 
exit of the imago leaves no disturbance behind”? (p. 63). 
The most interesting question, of course, is, how far 
care and industry can improve this imperfect natural 
wealth. The strongest proof of the value of such educa- 
tion is to be found in the fact that the beautiful Italian 
and French silks, whose fineness and regularity insure 
for them a price 50 per cent. higher than the best China 
silks, are the lineal descendants of the eggs brought from 
China in the reign of Justinian. The destruction caused 
among them by the dreadful disease, pebrine, has neces- 
sitated the import into Europe of Japanese eggs, the 
drabby colour of the silk of which marred all the efforts 
of the dyer to obtain clear delicate tints, especially in 
different shades of white; but careful attention and arti- 
ficial selection are bringing them near to equality with 
the pure European silk; and Major Coussmaker in 
Pooneh has succeeded in obtaining perfectly white Tusser 
silk by causing the caterpillar to void all its excrement 
before spinning. 
The special fitness of Tusser silk for the dark dull 
colours now fashionable is most optimistically expressed 
by Mr. Wardle in the phrase that “ Tusser silk properly 
dyed inherently takes shades of artistic merit?’ Is dirt 
then beauty? and purity and brilliancy essentially vulgar? 
There can be little doubt that European skill and ma- 
chinery would more than balance the cheapness of Indian 
labour, which could be trusted to produce only the com- 
monest qualities of thrown silk. It is also far safer and 
less likely to end in failure or discouragement to make 
spun silk the object of Indian produce than to attempt to 
rival the beautiful productions of Italy and China. 
One cannot help noticing with satisfaction in this con- 
cise history the working together for good of such widely 
separated parties as, in India, the high Government official, 
the investigating naturalist, the active military officer in 
charge of a district ; then the organising British manu- 
facturer, who brings into willing co-operation the Italian 
throwster, the Leek dyer, the Halifax weaver, the London 
artist, not to mention the taste and skill of the lady- 
bountiful of her neighbourhood. W. ODELL 
NOTES 
On Tuesday evening, April 11, the public thoroughfare 
stretching between Hatton Garden and the Old Bailey was 
lighted for the first time by the electric light. The novelty of 
the installation was the fact that the incandescent system had 
been adojted in preference to the arc system. Mr. E. Hi. 
Johnson, the agent of the Edison Electric Light Company, has 
in fact made a public demonstration of the Edis-n system by 
lighting up a district of London in the same way as by gas. 
In addition to the street lights, the different premises lining the 
street are also lighted ; for example, the City Temple Church, 
Messrs. Nezretti and Zambra’s, Messrs. Spiers and Pond’s. In 
all there are 936 incandescent lamps, and these are fed by one of 
the large dynamos stationed at No. 57, Holborn, the distributing 
centre of the company. These large generators are made 
upon the same plan as the smaller ones recently described 
by us, and are driven by Porter engines. They yield a 
current of 1025 ampéres. The resistance of each lamp white- 
hot is 140 ohms, and as this is much greater than the hot 
resistance of other incandescent lamps, the resistance of a 
long circuit is not so relatively high as in other systems, and 
hence there is less need of large leads. The cost of copper for 
conductors is an important item in electric lighting, but should 
copper conductors become too expensive to use, Mr. Edison 
intends to employ iron, say old iron rails. Mr. E. H. Johnson 
states that the company intend to manufacture and supply elec- 
tricity for all kinds of purposes, and judging from experience 
gathered in New York, where a district is lighted by this system, 
the profits from the sale of electricity for power purposes alone 
will pay the company’s dividends, so that they can afford to 
give the light for nothing. This remark is a rejoinder to those 
