To prepare the ♀ for this Work.
TAke Arsenick one part, decrepitated Salt two parts, pulverize and mix them to∣gether; then stratifie with this Powder some thin Plates of ♀, cement them for two days, then put them to a strong {fire} for six hours; then wash these Plates from the Salts, and beat them to Powder, wash the Powder with Vinegar, and then with {water} two or three times; then with Soap make a Paste thereof, which put in a Crucible, that hath a hole in the bottom, put this Crucible in another Cruci∣ble, and so melt down the Powder of ♀, and it will run through the hole into the other Crucible, and you shall have a very white ♀, and well prepared for Projection.