a dark brown color; a solution of iodine has a similar effect.
The brown portions of the joints are nitrogenous in character; cotton
fibers are devoid of nitrogen.

[Illustration: Figs. 1, 2, 3, 4, 5.]

EXPERIMENTS WITH FLAX.

A chemist of the Department of Agriculture had once occasion to make
experiments with flax fibers, his object being to make them chemically
pure; and to this end he treated them with excess of bleaching agents,
thus rendering them of a beautiful white, silky appearance, to the naked
eye; but when I examined them under the microscope, I found the brown
nitrogenous matter of the joints still present, and on using the chromic
acid test, they became deeply stained. A chemical solution of flax
therefore would prove for some purposes undesirable, owing to the
presence of this ligneous matter. A chemical solution of cotton which is
destitute of ligneous matter will give a chemically pure solution. Cotton
is therefore better adapted than flax for collodion compounds.

WOOL TESTED WITH ACID.

It is known that when wool is treated with the sulphuric acid of commerce
or in strong dilute sulphuric acid, the surface scales of the fiber are
liberated at one end, and appear, under a low power, as hairs proceeding
from the body of the fibers. Wool may remain thus saturated in the acid
for several hours, without appearing to undergo any further change, as
far as is revealed by the microscope. When treated in mass in a bath of
sulphuric acid, strength 60 deg. B., for several minutes, and afterward
quickly washed in a weak solution of soda, and finally in pure water and
dried, it feels rough to the fingers, owing to the separation of the
scales. I have preserved a small quantity of wool thus treated for the
last twelve years, my object being to ascertain whether the chemical
action to which it was exposed would impair its strength. As far as I can
observe, without the aid of the proper tests, it seems to have retained
its original tenacity. Wool thus treated seems to possess the property of
resisting the ravages of the larvae of the moth. This specimen, although
openly exposed for the period named, suffered no injury from them. Under
the microscope, the lubrications appear to have resumed their natural
position, and appear finer.

From these experiments it would seem not improbable that a new article of
commerce might be produced from wool thus treated, considering that it
seems to be moth-proof.

I fin