How letters are made, that eat the paper.

If you mingle oyl of Vitriol with common ink or any other black colour, in few days by corroding the paper, or the ink it self, the letters will vanish, or in a moneth, as you put in more or less of the oyl; and this you may try before you send away your letter: If you would have it work more slowly, add but a little oyl; if faster, put in more: you may, when it is too strong, put some water to it. The same is performed, if you mix a strong lye, they call it the Capital, with your ink; for first they will be yellow, and then they will vanish. The same is done by oyl of Tartar, or Salt Alkali, or Soda, and strong water of separation of Gold; for these corrode the letters, and the paper, that nothing of the letters will appear. If you desire to know