Point I

They who Engrave or Etch upon Copper, may of this subject prepare a good corrosive Water, by which (the Copper Plates being first smeared over with a Covering fit to defend them, and what Images or Lines they please, drawn upon them, with a stile or stift) by an easie and compendious manner, they will be eroded or eaten, which otherwise would require a long time to be engraven.

That a corrosive and graduating Aqua-fortis may be prepared of Nitre by destillation, needs no proof, the way of making it being every where known, as a thing common, only here it is proved, that this shortening of the Engraver’s Work may be performed by the Salt of the Earth.