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VI. History of Colours.

PART I.

Of Black.

LACK, a colour in many cases the most important,and in its use the most extensive, of all those whichart is concerned in preparing or applying, is chosen

which will be occasionally continued in the prosecution of

The practices of the workmen in one branch of colour-ing are generally little known to those who are employedin another; the several methods of applying even onecolour, on different kinds of bodies, being the objects of somany distinct arts, each of which has its own rules ofworking, peculiar to itself, and established by long custom.

Of the arts of communicating a black colour to diffe-rent subjects, there are some which have made great ad-vances towards perfection, whilst others remain far moreimperfect, in regard not only to the dispatch and facilityof the execution, but likewise to the beauty and durationof the colour. Thus woollen and silk are both dyed of apermanent deep black, but with this difference, that whatthe woollen dyer effects by three or four dippings of thecloth in his dying liquor, the silk dyer scarcely obtainsfrom twenty or thirty dips; whereas, on the contrary, thedyer of linen and cotton thread, however he prolongs theoperation, or repeats the dippings, is unable to communi-cate to the thread a blackness that shall endure wearing.Thus also the printer fixes upon paper an ink which con-

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tinues