149 
and nothing will contribute more to further their pro¬ 
gress but to improve the colouring of their wool and cotton 
goods. 
The art of the dyer has also been a great while neglected 
in Europe ; and abandoned as it has been in America, to the 
care of common practitioners, unguided by chemistry and 
untutored by taste, and as long as government suffered it to 
be so, it remained stationary ; but as soon as philosophy en¬ 
abled this art to draw from mineral, vegetable and animal 
substances their colouring particles, and to apply them un¬ 
changed through the mediation of proper mordants to 
wool, cotton, linen and silk, their manufactures have been 
vastly promoted. Colouring principles are useless if they 
are not rendered durable and unchangeable by proper mor¬ 
dants. Those mordants are different kinds of salts with 
which the dying principles are amalgamated, and their effect 
is such that colours which deprived of their mediation would 
change when exposed to the air, or would be washed away, 
are by them set and fixed so steadily, that even vegetable 
acids cannot alter them. 
The vitriolic, aluminous, and alkaline salts had for many 
years been used as mordants, but none of those substances 
have been universally successful for all sorts of colours, and 
they have altogether failed to make the true scarlet. But by 
the ingenuity of the French chemists employed to superin¬ 
tend the royal manufactory of the Gobelins, that valuable 
colour, the secret of which was thought to have been buried 
under the ruins of Tyre, was procured : Macquer used for 
that purpose the solution of tin by the aqua regia, and 
with the same mordants he engendered a variety of other 
handsome red colours, from cheaper and more common in¬ 
gredients, extracted from the vegetable and animal king¬ 
dom. The Asiatics who are not acquainted with the use of 
that solution, employ with great advantage as a mordant, 
a solution of fixed alkali or soda with a solution of al¬ 
um, and I am satisfied that the same mordant applied to 
O 
