Mr. Upham informs that this Town of Brookfield abounds with a Stone, out of which Allum, Coperas and Sulphur are made. Out of one Bushell of this Stone, he made five Pounds of Coperas. He put the Stone into a Tub, poured Water on it, let it Stand 2 or 3 days, then drew it off, and boiled the Liquor away—let it stand and it shot into a Kind of Christals. Adding Chamberly1
and Alkaline Salts to the Coperas and that makes Allum.
We made some Sulphur, by Sublimation. We put 4 Quarts of the Stone into an Iron Kettle, laid a Wooden Cover over the Kettle leaving an Hole in the Middle. Then We put an Earthern Pot over the Top of the Kettle, and cemented it with Clay—then made a fire under the Kettle, and the Sulphur sublimated. We got about a Spoonfull.2
We have found a Bed of yellow Ocre in this Town. I got 12,00 Wt. We make Spanish Brown by burning the yellow Ocre.