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wastung, unless the paper admits them to fink into itssubstance. The ancients were not insensible of this im-perfection, and sometimes endeavoured to obviate it,according to Pliny, by using vinegar, instead of water, fortempering the mixture of lamp black and gum. I triedvinegar, and found it to be of some advantage, not as givingany improvement to the cement, but by promoting thesinking of the matter into the paper. As this washingout of the ink may be prevented, by using a kind of papereasy enough to be procured, it is scarcely to be consideredas an imperfection; and indeed, on other kinds of paper,it is an imperfection only so far as it may give occasionto fraud, for none of these inks are in danger of beingotherwise discharged than by design. The vitriolic inksthemselves, and those of printed books and copper plates,are all dischargeable; nor can it be expected of the inkmaker to render writings secure from frauds.

Our experiments and reflections on inks having thus ledus back to the practice of the ancients, a further improve-ment occurred, that of uniting the ancient and moderninks together; or using the common vitriolic ink, insteadof water, for tempering the ancient mixture of gum andlamp black. By this method it should seem that thewritings would have all the durability of those of formertimes, with all the advantage that results from the vitriolicink fixing itself in the paper. Even where the commonvitriolic mixture is depended on for the ink, it may inmany cafes be improved by a small addition of the ancientcomposition, or of the common Indian ink which answersthe fame purpose: when the vitriolic ink is dilute, andflows so pale from the pen, that the fine strokes, on firstwriting, are scarcely visible, the addition of a little Indianink is the readiest means of giving it the due blackness.By this admixture it may be presumed also that the vitriolic

ink