The direct source of the nitrogen contained in plants is an unsolved mystery, though the ultimate source of much of it must be the atmosphere. A wheat crop gave on unmanured land from 15.9 to 25.2 pounds of nitrogen, per acre, yearly, but the amount found in the rainwater of the same district was only from 6.23 to 8.58 pounds per acre. Singular to say, the use of a fertilizer, called a "complex mineral manure" in the reports, added only about two pounds of nitrogen per acre. But the case is altered when potassic manure is used, and especially when applied to land bearing beans. Such a crop gains 13½ pounds of nitrogen by the addition of saltpetre, or 28 per cent. A similar result was obtained with clover—a leguminous crop. A potassic fertilizer increased the yield of nitrogen one-third. One of the anomalies observed in the study of plant growth is that a good crop instead of exhausting the soil seems to improve it. The better the crop, and the more nitrogen removed, the better will the succeeding crop be. Thus clover removes a much larger amount of nitrogen than wheat, the quantity being on unmanured land, say 30.5 pounds per acre for clover and 20.7 pounds for wheat, and yet the wheat crop is improved if clover is occasionally interpolated or a fair rotation of crops kept up. In 1874 barley succeeding barley gave 39.1 pounds of nitrogen, while barley following clover gave 69.4 pounds of nitrogen withdrawn from an acre of soil. These amounts take no account of the nitrogen carried off by the drainage of the soil, which analysis of drainwater proves to be considerable. The source of all this nitrogen is undoubtedly the atmosphere, but the mode of conveying it into the soil is unknown.
IMPORTANT PREHISTORIC DISCOVERIES.
Few persons are aware of the wealth of what are called "prehistoric" remains. The finding of an isolated skeleton, in a cave, with stalagmite completely covering it, is accepted as an occurrence that is not very remarkable. However ancient it may be, the preservation of the bones is exceptional. But a late discovery in France, near Hastiére-sur-Meuse, is of much more importance. No less than fifteen burial caverns were found, and from the five that have been explored no less than fifty-five human skeletons have been taken, among which are thirty-five well-preserved skulls.
In addition to these "finds" the plateaux yielded sixteen dwelling places of the old inhabitants from which have been taken a quantity of stone implements. These show the age of the skeletons to be that of the polished, or "new" stone period. The prospect of being able to restore the men who lived before the earliest recorded dates is now very good. Some hundreds of their skeletons, with a valuable series of skulls and enormous collections of their handiworks, are now in the museums of the world.
Some of the more remarkable of these discoveries have been alluded to at different times in this Miscellany. One of the latest and most interesting consists of some pointed sticks, found in a Swiss coal bed, the pointing having been done by hand. It may be thought difficult to establish so remarkable a fact in a mass of coal in which the rods have been pressed flat and perfectly carbonized. But a microscopic examination of one of these pieces shows that the fibres of the wood run in two different directions, the two systems meeting at an angle. One of the sticks has had its end shaved down, the cut surface being then applied to the other, and some substance, probably bark, being wound around the joint. The marks of this wrapping are perfectly distinct, and in one case the wrapping itself remains. As the bark used for this purpose was different from the natural bark of the rods, the microscope is now able to distinguish between the two, though both are turned to coal. Descriptions and illustrations of these interesting relics are published in the "Primeval World of Switzerland," by the celebrated Professor Heer. There is no doubt they formed part of some basket work. Their age is still doubtful, but must be very great.
THE PHYLLOXERA CONQUERED.
The investigation instituted by the French Academy of Sciences into the best means of destroying the phylloxera, or grapevine pest, has ended in the conclusion that the sulpho-carbonates are a complete antidote to these destructive insects. This result has already been announced in this Miscellany, and it only remains to explain the action of these salts. Under the influence of carbonic acid, which is always present in soils containing organic substances, they decompose. A carbonate is formed, and sulphuretted hydrogen and bisulphide of carbon are evolved. Both of these are deadly poisons to the phylloxera as well as to man. To complete the fitness of these salts to agricultural uses, the sulpho-carbonate of potassium has an excellent effect upon the vines, potash being one of the most valued constituents of manures. Success in using the antidote depends upon bringing it in contact with every part of the root-system of the plant. This can be done by dissolving the salt, but it is better to mix it with half its weight of lime and sprinkle it on the ground at the beginning of the rainy season, which in France lasts from October to March. M. Mouillefert, who examined this subject under direction of the Academy, reports that as an antidote the sulpho-carbonates are a proved success, and nothing now remains but to educate the vine growers to their proper use. This subject has peculiar interest to Americans, for the phylloxera is our evil gift to France. It is matter of common observation, both in animal and vegetable physiology, that one race or species may live in comfort with an enemy—be it a disease or a parasite—which is destructive to other species. The American vineyards are by no means free from the phylloxera. On the contrary, they are full of this insect, but the vines do not lose their hardiness in consequence. They flourish in spite of their enemy.