Page:Popular Science Monthly Volume 34.djvu/729

Rh there are about 172,000 acres of land under vine-cultivation in north and south Bulgaria. The yield of wine per acre varies between 250 and 350 gallons, two thirds of which is red wine and the remainder white. The wine in some vineyards is said not to be inferior to the best natural wines of other European countries. In 1886 some 140,000 gallons of wines were exported from southern Bulgaria to the south of France. There they were manipulated and sold as the products of the country. The phylloxera made its appearance a few years ago, but stringent measures were at once taken to stamp it out, and very strict regulations are enforced to prevent its return.

The Chemistry of an Egg-Shell.—The shell proper of an egg is made up mostly of earthy materials. The proportions vary according to the food of the bird, but ninety to ninety-seven per cent is carbonate of lime. The remainder is composed of from two to five per cent of animal matter and from one to five per cent of phosphate of lime and magnesia. Now, Mr. P. L. Simmonds asks, where does the hen procure the carbonate of lime with which to form the shell? If we confine fowls in a room, and feed them with any of the cereal grains, excluding all sand, dust, or earthy matter, they will go on for a time and lay eggs, each one having a perfect shell, made up of the same calcareous elements. Vauquelin shut up a hen for ten days, and fed her exclusively upon oats, of which she consumed 7,474 grains in weight. During this time four eggs were laid, the shells of which weighed nearly 409 grains; of this amount 276 grains were carbonate of lime, 17 grains phosphate of lime, and 10 grains gluten. But there is only a little carbonate of lime in oats, and whence could this 409 grains of the rocky material have been derived? The answer to this question opens up some of the most curious and wonderful facts connected with animal chemistry. The body of a bird, like that of a man, is but a piece of chemical apparatus, made capable of transforming hard and fixed substances into others of a very unlike nature. In oats there is contained phosphate of lime, with an abundance of silica, and the stomach and assimilating organs of the bird are made capable of decomposing the lime-salt and forming with the silica a silicate of lime. This new body is itself made to undergo decomposition, and the base is combined with carbonic acid, forming carbonate of lime. The carbonic acid is probably derived from the atmosphere, or more directly perhaps from the blood. These chemical changes among hard inorganic bodies are certainly wonderful when we reflect that they are brought about in the delicate organs of a comparatively feeble bird, under the influence of animal heat and the vital forces. They embrace a series of decomposing and recomposing operations which it is difficult to imitate in the laboratory.

Fresh-Water Sponges.—The fresh-water sponges, according to Mr. Edward Pott's monograph, resemble in constitution and general appearance many of the sponges of a marine habitat, with the addition that they have gemmules or "seed-like bodies," which marine sponges have not. They are green, but may be distinguished from mosses and Confervæ by the difference between smooth, slender threads and leaves; by the presence of efferent or discharging apertures; and, with a lens, by their spicules—to which finding the spherical gemmules adds further confirmation. The green color varies according to the light, and may, in dark places, or dark parts of the sponge, be faded into nearly white, gray, or cream color; but some species are never green in the sunlight. These organisms have occasionally been discovered growing in water unfit for domestic uses; but as a rule they prefer pure water, and in the author's experience the finest specimens have always been found where they were subjected to the most rapid currents. "The lower side of large, loose stones at the 'riffs' or shallow places in streams; the rocks amid the foaming water at the foot of a mill-dam fall; the timbers of a sluice-way, the casing of a turbine water-wheel, or the walls of a 'tail-race' beneath an old mill—in all these places they have been found in great abundance and of a very lusty growth. Of all discouraging situations it is almost hopeless to look for them in shallow water having a mud bottom. . . . In any body of water liable to be charged with sedimentary material, the principle of natural selection favors those growing on the lower