Instead of nitric acid we may use strong acetic acid to dissolve the cotton. The resulting cellulose acetates are less inflammable than the nitrates, but they are more brittle and more expensive. Motion picture films made from them can be used in any hall without the necessity of imprisoning the operator in a fire-proof box where if anything happens he can burn up all by himself without disturbing the audience. The cellulose acetates are being used for auto goggles and gas masks as well as for windows in leather curtains and transparent coverings for index cards. A new use that has lately become important is the varnishing of aeroplane wings, as it does not readily absorb water or catch fire and makes the cloth taut and air-tight. Aeroplane wings can be made of cellulose acetate sheets as transparent as those of a dragon-fly and not easy to see against the sky. The nitrates, sulfates and acetates are the salts or esters of the respective acids, but recently true ethers or oxides of cellulose have been prepared that may prove still better since they contain no acid radicle and are neutral and stable. These are in brief the chief processes for making what is commonly but quite improperly called "artificial silk." They are not the same substance as silkworm silk and ought not to be--though they sometimes are--sold as such. They are none of them as strong as the silk fiber when wet, although if I should venture to say which of the various makes weakens the most on wetting I should get myself into trouble. I will only say that if you have a grudge against some fisherman give him a fly line of artificial silk, 'most any kind. The nitrate process was discovered by Count Hilaire de Chardonnet while he was at the Polytechnic School of Paris, and he devoted his life and his fortune trying to perfect it. Samples of the artificial silk were exhibited at the Paris Exposition in 1889 and two years later he started a factory at Basancon. In 1892, Cross and Bevan, English chemists, discovered the viscose or xanthate process, and later the acetate process. But although all four of these processes were invented in France and England, Germany reaped most benefit from the new industry, which was bringing into that country $6,000,000 a year before the war. The largest producer in the world was the Vereinigte Glanzstoff-Fabriken of Elberfeld, which was paying annual dividends of 34 per cent. in 1914.