Tum~ENT "1 ยข)PICS.
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DYEING UF \O()L.--The authur agrees with tim theory that wool contains amino, imino, and carboxyl groups, as only by this constitution can it be explained why wool mordanted with tin tannate loses its affinity for acid dyestuffs. This loss of affinity also occurs when hydroxyl and carbonyl groups are introduced by the dyestuffs, etc., used. (,5l. Saget, Monit. Sci., e4, 8o.) ETYM(AA)GY AND IIIST(}RY OF "J'HIยข WORD 'GAS.'--J. B. van ttelmont was the first to differentiate the aeriform substances (which behave differently), from common air and vapors, and these he arbitraril 3 called 'gases.' No reason can be assigned for the point of view which led him to coin this word; from a comparison with the ' Diinste' (vapors) and the 'chaos' of the old authors. N~ hint can be drawn as to its etymological derivation from the word chaos. Von Lippmann states that the word chaos expressed in antiquity the origin of all things. The author proceeds to describe the labors of other investigators to determine the etymology of the expression ' gas,' from the time Van Helmont coined it, which has remained the same to the present day, in spite of manifold and great changes in the idea. (~[ax Sheter, ('hem. Zt.ยข., 34, t93-~94.) EXPI.OSIVI~; COAL DUST.--Recent experiments have proved conclusively that coal dust which is so fine as to pass a 2oo mesh sieve, will explode on contact with either a naked flame or with the arc of an electric current. (5~ci. American, Feb. 26,