in Ireland, which had long lain undisturbed, when plowed, produced an extraordinary crop of corn poppies. He thought that the physical texture of the soil would probably account for the long period during which the seed must have lain dormant. It seemed that in hard, closely packed soil seeds could remain in the resting state, but that they would assume their vital condition as soon as the soil was loosened. Another gentleman said that this power of seeds to germinate after a dormant period threw light on the glacial theory, since the seeds might possibly have remained buried in the quiescent state and then have germinated after the flow of ice had reached farther south.
Uses of Sawdust.—The most usual and extensive use of sawdust is probably as an absorbent on floors and in spit-boxes, but it has found many other economical applications. Compressed with pitch or with its own intrinsic resin if it be very resinous, it forms excellent kindling blocks; it may be burned as a fuel in specially prepared fireplaces. Fuel blocks are made by compressing it with various substances. An artificial hard wood is mentioned as formed in this way. At some factories it is distilled for purposes of lighting and the ammoniacal by-products. Oxalic acid is made from it by the process of Capitaine and Herlings. It forms a valuable litter for stables, and has fertilizing qualities of its own. Eggs are preserved by being carefully packed in it. With albumin, liquid paste, alum, bichromate of potash, or molasses it makes excellent briquettes; with cement, lime, or gypsum, a material for constructions; and with slaked lime, an excellent mortar. Mixed half and half with sand and clay, a material for partition walls and ceilings is formed. Sawdust is, therefore, a very useful material.
First Uses of Gunpowder.—The invention of gunpowder is shown by Mr. Oscar Guttmann, in his book on the Manufacture of Explosives, to have been most probably an evolution. The Greek fire of naphtha, mentioned by early European and Arabian writers, is believed to have been a composition containing niter, sulphur, and charcoal. Marcus Græcus, who wrote in the tenth century, gives a composition for charging rockets and crackers closely approaching that of modern blasting powder. This receipt is quoted by Albertus Magnus, and another one, not so clear, is given by Roger Bacon. None of these writers, however, speak of the use of such substances in any way like the firing of projectiles from guns; on the contrary, they all describe crackers and bombs or maroons, and say that these were discharged into towns from ballistæ or catapults or mangonels for the purpose of setting fire to them. Mr. Guttmann has found, however, in the Wardrobe Accounts of King Edward III of England, an entry between A.D. 1345 and 1349 giving credit to one Thomas of Roldeston for the king's work for his guns, for nine hundred and twelve pounds of saltpeter and eight hundred and eighty-six pounds of live sulphur. This seems to confirm the tradition that guns were used by the English at the battle of Crécy in 1346. Mr. Guttmann decides that Berthold Schwartz invented this use of gunpowder about 1313; if so, Schwartz must have been very young at the time, or else have lived to a very great age, for the date of his death is given as 1384.
French Mushrooms.—Mushroom-growing in France is a matter of ancient history, and the variety of mushrooms is infinite. The industry originated in a peculiar way. When the French began to make beds for their melons they noticed that large numbers of mushrooms would suddenly appear on the little mounds. They proved as profitable as the melons, but a crop could not be depended on. A number of investigators went to work to discover methods by which a fairly certain and regular crop could be obtained. They have partially succeeded, and the result is an industry very profitable to all concerned, and a consumption of mushrooms in France which is now something enormous. The mushroom loves a cool, damp place, and light has a decided effect upon its color, sunlight turning the surface to a reddish brown. It is for these reasons that it is usually cultivated in caves. In the department of the Seine there are over three thousand of these subterranean truck gardens, most of them de-
