You will have perceived by the Act of the last session, entitled an Act making further provision for the payment of the debts of the United States,1 that after the end of the present month the duties on distilled spirits are regulated according to certain classes of proof, to be determined by Dycas’s Hydrometer. Doubting whether it might be convenient to the several officers of the Customs to procure for themselves this instrument, I have taken measures for the purpose. One I now send accordingly. Fahrenheits Thermometer, which is a necessary part of the Apparatus, is however still wanting; but I presume it will not be difficult for each officer to procure one at the place of his residence, which may answer tolerably well till others, of a more convenient size, can behad; those generally to be met with being rather too large to be as quickly affected by the temperature of the liquor as the dispatch of business requires.

Inclosed are directions for using the Hydrometer,2 which, it is hoped, are sufficiently particular & clear to be readily understood & applied. I am at the same time sensible that embarrassments & delays will attend the process in the beginning, but I trust practice will overcome them.

Lest however that should not be the case, I have taken measures for providing a Substitute, which will admit of a more summary proceeding. Directions for the use of this instrument are also inclosed. It is my intention that there shall be at each Port one of each kind; the substitute for common use, and the Original as a standard or check, but it is not possible, in the first instance, to send both. Hence one only will accompany this letter.

It may serve to aid the officers to be informed that the first of the classes of the proof mentioned in the law corresponds with Gin, the second with St Croix rum, the third with Antigua rum, the fourth with Jamaica spirits, the fifth with the usual strength of high wines, & the sixth or last with what is called Alcohol.

I take it for granted that particular care will be used to avoid any inconveniences or unfavorable impressions from the novelty of the arrangement; as the success of it cannot fail to add materially to the security & efficacy of the revenue, and at the same time to render the duty more equal & equitable.

It is my wish that peculiar attention be paid to the accuracy of each instrument, & to the correspondency between the two. It is apprehended to be probable that the apparent temperature of the air to the feeling, or at least its temperature, as marked by the Thermometer, will be a sufficient guide in the use of the instrument designed as a substitute. If so it will supercede the necessity of ascertaining every time the precise temperature of the liquor by the actual immersion of the Thermometer.

But it will not do to rely upon this till Experience, after a number of trials, shall have evinced the fact.

You will, of course, communicate to me, from time to time, such observations concerning the matter as shall be suggested by the course of practice.

I am, Sir, Your Obedient Servant.