By the Excise laws at present existing in this country, the various degrees of strength of brandy, rum, arrack, gin, whiskey, and other spiritous liquors, chiefly composed of little else than spirit of wine, are determined by the quantity of alcohol of a given specific gravity contained in the spiritous liquors of a supposed unknown strength. The great public importance of this subject in this country, where the consumption of spiritous liquors adds a vast sum to the public revenue, has been the means of instituting many very interesting series of experiments on this subject. The instrument used for that purpose by the Customs and officers of Excise, is called Sikes's hydrometer,[88] which has now superseded the instrument called Clark's hydrometer, heretofore in use.
The specific gravity or strength of the legal standard spirit of the Excise, is technically called proof or proof spirit. "This liquor (not being spirit sweetened, or having any ingredient dissolved in it, to defeat the strength thereof,) at the temperature of 57° Faht. weighs exactly 12/13th parts of an equal measure of distilled water;" and with this spirit the strength of all other spiritous liquors are compared according to law.
The strength of spirit stronger than proof or over proof, as it is termed by the revenue officers, is indicated by the bulk of water necessary to reduce a given volume of it, to the legal standard spirit, denominated proof—namely; if one gallon of water be required to bring twenty gallons of brandy, rum, or any other spirit, to proof, that spirit is said to be 1 to 20 over proof. If one gallon of water be required to bring 15, 10, 5, or 2 gallons of the liquor to proof, it is said to be 1 to 15, 1 to 10, 1 to 5, and 1 to 2, over proof.
The strength of brandy, rum, arrack, gin, or other spiritous liquors, weaker than proof, or under proof, is estimated by the quantity of water which would be necessary to abstract or bring the spirit up to proof.
Thus, if from twenty gallons of brandy one gallon of water must be abstracted to bring it to proof, it is said to be 1 in 20 under proof. If from 15, 10, 5, or 2 gallons of the liquor, 1 gallon of water must be abstracted to bring it to proof, it is said to be 1 in 15, 1 in 10, 1 in 5, and 1 in 2 under proof.
It is necessary to understand this absurd language, which is in use amongst the officers of Excise and dealers in spirit, in order to know what is meant in commerce by the strength of spiritous liquors of different denominations. And hence, for the business of the exciseman, a table has been constructed, expressing the strength or specific gravity of mixtures of different proportions of spirit and water, at different degrees of temperature; and according to this table the duty on spirit is now levied.
Brandy and rum is seizable, if sold by, or found in the possession of, the dealer, unless it possesses a certain strength.[89] The following are the words of the Act:
"No distiller, rectifier,[90] compounder or dealer, shall serve or send out any foreign spirits, of a lower strength than that of 1 in 6 under hydrometer proof,[91] nor have in his possession any foreign spirits mixed together, except shrub, cherry or raspberry brandy, of lower strength than as aforesaid, upon pain of such spirits being forfeited; and such spirits, with the casks and vessels containing the same, may be seized by any officer of Excise."
We have, therefore, a ready check against the frauds of the dishonest dealers, in spiritous liquors. If the spirit merchant engages to deliver a liquor of a certain strength, the hydrometer is by far the most easy and expeditious check that can be adopted to guard against frauds of receiving a weaker liquor for a stronger one; and to those individuals who are in the habit of purchasing large quantities of brandy, rum, or other spiritous liquors, the hydrometer renders the greatest service. For it is by no means an uncommon occurrence to meet with brandy, rum, and other spiritous liquors, of a specific gravity very much below the pretended strength which the liquor ought to possess.