_a._ With SYKES’ HYDROMETER. _Revenue system._ The _engraving_ below represents Sykes’ hydrometer, as made by Mr Bate, under the directions of the Commissioners of Inland Revenue and Customs. It consists of a spherical ball or float, with an upper and lower stem, and is made of brass, which (in the more expensive instruments) is usually coated with gold, to prevent corrosion from damp, and the acidity so generally present in spirituous liquors. The upper stem (A) is about four inches long, and is divided into ten parts, each of which contains five subdivisions. There are nine movable weights of the form _b_, of different sizes, numbered respectively 10, 20, 30, &c., to 90, each of which represents so many of the principal divisions of the stem, as its number indicates. In use, one of these weights is slipped on to the lower stems; and thus, by means of them, the instrument acquires a range of above 500 divisions, or degrees, extending from the Revenue ‘standard alcohol’ (sp. gr. ·825) to water. It is so formed as to give the sp. gr. with almost perfect accuracy, at 62° Fahr. When loaded with the weight 60 it sinks in proof spirit to the line marked (P) on the narrow edge of the stem at 51° Fahr.; and, by further placing the square weight or cap (also supplied with the instr.) on the top of the upper stem, it floats exactly at the same point in distilled water. This weight or cap is found to weigh 43·66 grs., which is practically 1-12th of the total observed weight of the instrument, and its poise 60, and hence shows the difference between the gravity of proof spirit and water, as explained hereafter. The whole is fitted up in a neat mahogany case, accompanied with a thermometer, and a book of tables containing corrections for temperature, &c.——_Process._ A glass tube of the form of fig. _B_ is filled to about the mark (_a_) with the sample for examination; the thermometer is then placed in the liquor, and stirred about for two or three minutes (observing not to breathe upon the glass, nor hold it in the hand), and the temperature noted. The hydrometer is next immersed in a similar manner, and gently pressed down in the liquor to the 0 on the stem with the finger; it having been previously loaded with any one of the nine weights that will cause it to float with the surface of the spirit at some point on the graduated part of the scale. The indication at the point cut by the surface of the liquor, as seen from below, added to the number of the weight with which the float is loaded, gives a number which must be sought in the hook of Tables, which is always sold with the instrument. In this book, at the page headed “Temperature as observed by the Thermometer,” and against the part of the column appropriated to the given indication (weight), will be found the strength per cent., expressed in degrees over or under proof, by VOLUME, in whole numbers or decimal parts. In reading off the indication, to ensure