A standard for skimmed milk may readily be fixed, by saying what strength the common saleable skimmed milk shall be by the lactometer, or what its specific gravity shall be in relation to that of water in the temperate degree of heat, and that an easy comparison may be made between the specific gravity of any milk, and its lactometer strength; this instrument is so constructed, that one of specific gra vity shall exactly correspond with three of strength ; that is, the strength of 90 by the lactometer is a milk whose specific gravity is 1030, to common pump water 1000. From a number of experiments and observations, it is ob servedethat the common saleable skimmed milk in Liver pool is from 52 to 64 of strength, that of new milk from 70 to 80 ; but it woula be difficult to fix any standard for the latter, unless some mode could be devised to discover whether it was mixed with old milk or not. The only method would be, after fixing the strength of it, to try, by letting it stand, to discover if it produced that quantity of cream, which as new milk it might reasonably be expected to do.
Another lactometer, upon a different principle, has been recently constructed, at the desire of Sir Joseph Banks, by Mr. Thomas Jones, mathematical instrument maker, Cha ring Cross. Sir Joseph has described it in the Farmer's
Journal. and it promises to answer the intended purpose.
It consists of any number of glass tubes, of the same in ternal diameter, which is generally about one-third of an inch, and about 11 inches long. They are closed at one end, and open and a little flanched at the other, like the test tubes used by chemists, and are mounted on stands in the same manner. At the distance of 10 incites from the bot tom of each tube there is a mark, with 0, or zero, placed opposite it ; and from this point the tube is graduated into tenths of an inch, and numbered downwards for three inches, so that each division is of the tube. If several of the tubes are filled with new milk at the same time, and placed at the same temperature, the cake of cream will form at the top, and its thickness or quantity will be indicat ' ed by the divisions. In this way experiments may be made on the relative quantities of cream produced by different systems of feeding, or by different animals fed and placed under different circumstances. The per tentage of cream is thus obtained by simple inspection. Sea Brande's Jour nal. vol. iii. p. 393, 394.