Purified by this process, mercury not only permits of the motions of camphor on its surface, but renders visible the traces of the vapors that escape from it, and which resemble small tadpoles with a long tail that are endowed with very great agility. Nothing is more curious than to see the particle of camphor successively ascend and descend the strongly pronounced curves presented by the mercury near the sides of the vessel that contains it. On raising the temperature of the metal slightly, the motions of the camphor on its surface are accelerated, and the same effects occur with water that has been slightly heated. The experiments that we have just called attention to show what importance slight impurities may have upon certain results. "They prove," says our learned colleague Mr. Daquin, "that there exists upon polished substances an imperceptible coating of those fatty matters which serve to-day to explain Moser's images." We find therein also a manifest proof and a rational explanation of those grave errors into which the presence of these fatty matters, that have hitherto been scarcely suspected, led so clever and so distinguished a scientist as the illustrious discoverer of endosmosis.--_N. Joly, in La Nature_. * * * * * CARBONIC ACID IN BEER. We present a diagram, on exposition at the last Brewers' Convention in Detroit, of the racking device, devised by J. E. Siebel in 1872, and used at that time in the brewery of Messrs. Bartholomae & Roesing, in Chicago. The object of the apparatus is to retain as much carbonic acid in the beer as possible while racking the same off into smaller packages from the storage vats. The importance of this measure is apparent to every one who knows what pains are taken to preserve the presence of this constituent in all the former stages of the brewing process. In the method of racking off which is in present use in most breweries, the beer is forced through a rubber hose from the cask in the store vault to the barrels, kegs, and smaller packages in the fill room. Owing to the excess of pressure in the beer as it enters the keg, it is evident that a large amount of the carbonic acid gas must escape. The escape of carbonic acid during the process of racking off is indeed so large that even a small difference in the pressure of the atmosphere causes a remarkable difference in this respect. It is, therefore, evident that if a larger pressure can be maintained while racking off, a larger amount of carbonic acid gas will remain in the beer. It is true that the racking off will take a little longer time if done under pressure, but this inconvenience is certainly insignificantly small, when compared with the other labors and troubles daily undergone in a brewery, for the sole purpose to preserve in the beer the carbonic acid in that form in which it has been formed during the fermentation, and in which form it has far more refreshing and other valuable properties than in any