Modern Magic: A Practical Treatise on the Art of Conjuring

Perhaps this is the reason why it is called the “black art,” and was the cause of so much persecution in the “good old days,” when all was so pure and so virtuous, as the lovers of the beaux temps would have us believe. But pardon this digression. In the other bottle place a weak solution of the proto-sulphate of iron, about a half ounce to about a pint and a half of water. Have ready a bit of pyrogallic acid--about two-thirds of a tea-spoonful, wrapped in a small piece of blotting-paper that has been blacked with ink. Having completed these arrangements, and asserted that you have on the table a bottle containing water and another ink, you borrow a handkerchief, with which you cover the bottle containing the clear solution, and in doing so you slip into it the pyrogallic acid; and in handing the bottle to one of the audience to hold you give the contents a little imperceptible shaking. You then take another handkerchief and place it over the other bottle, which you hand to a person to hold. You then command the contents of each bottle to change places. Then, in removing the handkerchief from the ink bottle, you clutch the piece of string and quickly pull out the black wool and throw the handkerchief out of sight, showing the bottle to contain only water. You then ask the person holding the other bottle to remove the covering, when the fluid will be found to be “as black as night.” This trick always causes the greatest astonishment.