ry against its corrosive effects as arose when chlorine was
substituted for crofting. A great advantage was found to result from the
use of sulphuric acid, which was that a souring with sulphuric acid
required at the longest only twenty-four hours, and often not more than
twelve; whereas, when sour milk was employed, six weeks, or even two
months, were requisite, according to the state of the weather. In
consequence of this improvement, the process of bleaching was shortened
from eight months to four, which enabled the merchant to dispose of his
goods so much the sooner, and consequently to trade with less capital.

No further modification of consequence was introduced in the art till
the year 1787, when a most important change was initiated by the use of
chlorine (q.v.), an element which had been discovered by C.W. Scheele in
Sweden about thirteen years before. The discovery that this gas
possesses the property of destroying vegetable colours, led Berthollet
to suspect that it might be introduced with advantage into the art of
bleaching, and that it would enable practical bleachers greatly to
shorten their processes. In a paper on chlorine or oxygenated muriatic
acid, read before the Academy of Sciences at Paris in April 1785, and
published in the _Journal de Physique_ for May of the same year (vol.
xxvi. p. 325), he mentions that he had tried the effect of the gas in
bleaching cloth, and found that it answered perfectly. This idea is
still further developed in a paper on the same substance, published in
the _Journal de Physique_ for 1786. In 1786 he exhibited the experiment
to James Watt, who, immediately upon his return to England, commenced a
practical examination of the subject, and was accordingly the person who
first introduced the new method of bleaching into Great Britain. We find
from Watt's own testimony that chlorine was practically employed in the
bleachfield of his father-in-law, Mr Macgregor, in the neighbourhood of
Glasgow, in March 1787. Shortly thereafter the method was introduced at
Aberdeen by Messrs Gordon, Barron & Co., on information received from De
Saussure through Professor Patrick Copland of Aberdeen. Thomas Henry of
Manchester was the first to bleach with chlorine in the Lancashire
district, and to his independent investigations several of the early
improvements in the application of the material were due.

In these early experiments, the bleacher had to make his own chlorine
and the goods we