First, that, like Mr. Hooke’s Original, it requires, as one of its Constituents, a mysterious Substance; and as the nature of this Ingredient is not made clear, there is no way for Mr. Hooke’s result to be duplicated by any other Student of Chymical Arts [not the first time such a Gravamen could be leveled at that Author’s work—and perhaps sufficient Explanation of why he plaistered it up in a Wall].