161From John Adams to James Warren, 25 October 1775 (Adams Papers)
A Method of collecting Salt Petre from the Air which is talked of here is this. Take of Lime and Ashes equal Quantities, and of horse dung a Quantity equal to both the Ashes and Lime, mix them together into a Mortar, with this Mortar and a Quantity of long Straw to keep it together build two Walls Eighteen Inches thick, and three feet high, about four feet asunder. Then make a Center and turn...