86 
Silks and Silkworms. 
[February, 
them by means of an oxidising agent, and at first made use 
of permanganate of potash. The brown or orange colouring- 
matter was thus quickly destroyed, but the fibre of the silk 
was so much injured as to be unfit for spinning and weaving. 
He next tried barium peroxide, which in contact with water 
gradually gives off oxygen and destroys the colour. By this 
means it has been found possible to bleach the wild silks so 
that they can be dyed to the palest and most delicate shades. 
One drawback remains — the expense of the process. The 
cost of bleaching is 2s. per lb., which is a heavy charge for 
a material which does not itself cost more than ios. per lb. 
Acccordingly experimentalists, and above all Mr. Wardle, 
are seeking to introduce a process equally effective and more 
economical. The results already attained are understood to 
be highly promising, though the details cannot he made 
public till the process is rendered perfect and has been se- 
cured by means of letters patent. 
In the meantime Major Coussmaker, a diligent and skilful 
cultivator of wild silk, is turning his attention to preventing 
the silk from becoming coloured in the cocoon, so as to do 
away with the subsequent necessity for bleaching. It is 
known that the worm or caterpillar hardens its cocoon by 
means of a certain cement consisting of urate of ammonia, 
and being, in fact, of an excrementitious nature. Major 
Coussmaker writes : — “ This year, by opening the cocoons 
at various intervals, I was able to convince myself of the 
fadt that when the caterpillar has left off eating, and begins 
to spin, it voids 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 consistency of which depend upon the amount of vege- 
table 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 on 
which the caterpillar has fed, and with the state of the atmo- 
sphere at the time of spinning. The longer they remain 
coating the fibre, the harsher and the more discoloured it 
will be. It is therefore very necessary, I think, to remove 
this current at a very early date, and this chemistry has 
shown the manufacturers how to do. Before long fresh 
cocoons will be, at an early stage, thoroughly cleansed from 
all discolouring matter, and the Tasar silk will be available 
for manufacturing purposes as colourless as when first put 
forth by the caterpillar.” Major Coussmaker has sent Mr. 
Wardle a cocoon thus purified, and free from all brown or 
fawn colouration. 
