other form in which it may be subsequently introduced into the beer by artificial means. The apparatus designed in the accompanying cut is calculated to artificially produce a higher pressure of the atmosphere, at least within the keg which is to be filled with beer. For this purpose, the beer from the store cask running through the pipe, B, enters the keg through a hollow copper bung, fitting light into the bung hole by means of a rubber washer. The air contained in the keg, being replaced by the beer, is forced out by means of the hollow copper bung, taking its course through the pipe, inscribed "Glass Gauge," until it is allowed to escape in the standpipe, C, containing a column of water, the height of which designates the pressure within the keg, and a consequently increased retention of carbonic acid gas. If the keg or barrel is filled with beer, the same becomes apparent from the beer showing itself in the glass gauge; then the faucet, B, is closed, the copper bung is lifted out of the bung hole, and the beer contained in the pipe is just sufficient to completely fill the keg, which is then bunged up, while the apparatus is transferred to the next keg. Should the attendant carelessly neglect to close the faucet in proper time, the surplus beer will not necessarily be wasted, but will be collected in the vessel, D, whence it can be drawn off through e.--_Chemical Review_. [Illustration] * * * * * ON THE DIFFERENT MODIFICATIONS OF SILVER BROMIDE AND SILVER CHLORIDE. Hermann W. Vogel has made a comparative study of the properties of silver bromide, obtained by precipitation in an aqueous solution of gelatin, and those of the same compound prepared by precipitation in an alcoholic solution of collodion. In 1874 Stas called attention to six modifications of silver bromide. One of these, granular bromide of silver, obtained by boiling the flocculent precipitate for several days with water, he stated, was the most sensitive to light of all substances known; exposure for two or three seconds to the pale blue flame of a Bunsen burner being sufficient to blacken it. Important as this fact was for photographers it was not applied for years, and it was only in 1878, when, it having been found that silver bromide precipitated in a gelatine solution and boiled for several hours becomes much more sensitive to light, that the remarks of Stas was recalled. Today these observations have become of the greatest importance to practical photography. They have led to the preparation of the silver bromide gelatin emulsion and the silver bromide gelatin plates, which are twenty times more sensitive than the silver iodide collodion plates, and have become indispensable when impressions are to be taken in a dim light.