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tinues unaltered for ages, and which is not perhaps capa-ble of being changed by any natural agent that the paperitself can resist; while the common writing inks soonlose of their colour both on paper and on parchment, in-somuch that records, of no very long standing, have becomealmost entirely obliterated.

In the present history, I shall endeavour to trace, as faras my opportunities of information will enable me, thepreparation, production, and communication of black co-lours, through all the professions in which they are con-cerned ; that the artist, confined by his employment toparticular views, may be made acquainted with the me-thods, by which similar effects to those which he pro-duces, or wants to produce, are obtained in other arts, orin arts which in other respects differ from his own. Ex-periments, while they serve as a sure test for ascertainingthe respective facts, will often contribute at the fame timeto enlarge and render them more extensive; and likewiseafford means of distinguishing, in some complex opera-tions, the circumstances or materials essential to success,from the superfluous or injurious ones, which ignorance orchance perhaps at first introduced, and which prejudice orcustom have continued.

By thus examining and comparing the different me-thods, by which a similar colour is obtained or produced,and by which the several tinging materials are applied ondifferent subjects, I flatter myself that many of these arts,however disjoined- among different sets of workmen, willbe found to have natural and strong-connections, so thatan effective and useful commerce may be establishedamong them; that they will not only tend to illustrate*but mutually to improve one another; and that in manycases the practice of one art may be abridged or facilitated,its imperfections remedied, and its deficiences supplied, by

means,