decidedly duller when kept for some time in water at a temperature of
160° F., and the same wool, when subjected to boiling water at 212° F.,
became quite dull and lustreless. When tested for strength, the same
fibres which carried on the average 500 grains without breaking before
boiling, after boiling would not bear more than 480 grains." Hence this
third enemy is a boiling process, especially a long-continued one if
only with water itself. If we could use coal-tar colours and dye in only
a warm weak acid bath, not boil, we could get better lustre and finish.

We will now turn our attention to the chemical composition of wool and
fur fibres. On chemical analysis still another element is found over and
above those mentioned as the constituents of silk fibre. In silk, you
will recollect, we observed the presence of carbon, hydrogen, oxygen,
and nitrogen. In wool, fur, etc., we must add a fifth constituent,
namely, sulphur. Here is an analysis of pure German wool--Carbon, 49·25
per cent.; hydrogen, 7·57; oxygen, 23·66; nitrogen, 15·86; sulphur,
3·66--total, 100·00. If you heat either wool, fur, or hair to 130° C.,
it begins to decompose, and to give off ammonia; if still further heated
to from 140° to 150° C., vapours containing sulphur are evolved. If some
wool be placed in a dry glass tube, and heated strongly so as to cause
destructive distillation, products containing much carbonate of ammonium
are given off. The ammonia is easily detected by its smell of hartshorn
and the blue colour produced on a piece of reddened litmus paper, the
latter being a general test to distinguish alkalis, like ammonia, soda,
and potash, from acids. No vegetable fibres will, under any
circumstances, give off ammonia. It may be asked, "But what does the
production of ammonia prove?" I reply, the "backbone," chemically
speaking, of ammonia is nitrogen. Ammonia is a compound of nitrogen and
hydrogen, and is formulated NH_{3}, and hence to discover ammonia in the
products as mentioned is to prove the prior existence of its nitrogen in