Another Invisible Green Ink

Dissolve zaffre, in powder, in aqua regia, for twenty-four hours. Pour

the liquor off, and the same quantity of common water, and keep it in

a bottle well corked.

This ink will not be visible till exposed to the fire or the sun; and

will again be invisible when it becomes cold.

Another Electric Orrery See Page 92 Another Method facebooktwittergoogle_plusredditpinterestlinkedinmail