Treasury Department, June 1, 1791. “Your letter of the 24th Ultimo has been received. I approve the intention of the Surveyor to use generally the substitute for Dycas’s Hydrometer, the difference being so small. Yet, in any case, where that difference would convert one class of proof into another, Dycas’s must govern; unless it should appear by any imported Hydrometer of Dycas’s, which you may be able to borrow, that the other is more accurate, or unless it should better correspond with what is stated in the instructions for using those instruments, to be the usual proofs of spirits from different Islands.…”