Page:Popular Science Monthly Volume 4.djvu/526

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the action of water, air, and various gases. While some geologists had supposed that many of these, such as gneiss, greenstone, serpentine, talcose, and chloritic rocks, were igneous products, more or less modified by subsequent chemical action, others maintained that they were the result of aqueous sedimentation, and subsequently crystallized. This was the teaching of Hutton; and when early in the present century the crystalline rocks of the Alps were shown to rest on uncrystalline fossiliferous strata, it was suggested that the overlying crystalline strata were newer rocks which had undergone a metamorphism, to which those just beneath had not been subjected. This view spread until the great crystalline centre of the Alps was considered to be in part of secondary and even of tertiary age.

The author detailed the course of study by which he was led to question this view, and showed that there is no evidence in the Alps to support it; that Sedgwick and Nicoll had discredited the palæozoic age of the crystalline schists regarded by Murchison as Cambrian and Silurian; and, finally, gave the observations by which he had satisfied himself that the crystalline rocks of the Green and White Mountains, and their representatives in Quebec, New Brunswick, and on the Blue Ridge, were more ancient than the oldest Cambrian or primordial fossiliferous strata.

Tests for Glycerine.—The so-called pure glycerine of commerce, according to the Journal of Applied Chemistry, is often contaminated with metallic chlorides. Traces of ammonia are also sometimes present; and it not unfrequently contains oxalic acid or soda. The first-named impurity may be detected by diluting the glycerine with twice its volume of water and adding nitrate of silver. If the glycerine only becomes opalescent, the quantity of chlorides is not great enough to be injurious, but, if a flaky precipitate is produced, it indicates that the glycerine is unfit for medicinal use. To detect ammonia, mix the glycerine with its own volume of caustic potash, and bring a glass rod previously dipped in dilute muriatic acid over the mixture. If ammonia is present in injurious quantity, whitish vapors of chloride of ammonium will be formed. Oxalic acid may be detected, by adding lime-water, acetate of lime, or a mixture of chloride of calcium and acetate of soda. If the glycerine becomes turbid within five minutes after the reagent is added, it should be rejected. Traces of soda can only be revealed by evaporating the glycerine to dryness, and testing the residue.

American Origin of the Garden Raspberry.—Although the garden raspberry (Rubus Idœus) was imported from Europe, yet Dr. Asa Gray has lately made known some facts that would seem to make it certain that this plant, which is not indigenous to Europe, is a native of Japan and North America. Wild specimens from British America and the Rocky Mountains, it seems, must be referred by the botanist to the cultivated species, Rubus Idœus. Prof. Areschoug, who has devoted special study to the Rubi of Europe, concludes that this species did not originally have its home in Europe, but that its origin is to be found in the east of Asia, namely, Japan and the adjacent countries, and perhaps in North America. He also thinks that "the Asiatic and North American floras have reciprocally mixed with each other by passing Behring Straits and the islands which in its neighborhood form a bridge between the two continents."

Rapidity of Vegetable Growth.—A writer in the Gardener's Chronicle gives some illustrations of the prodigious activity manifested in the growth of plants during a few weeks. The process of growth, being gradual and noiseless, and moreover of everyday occurrence, is generally disregarded. And yet, what a quantity of water must be absorbed and exhaled, how much air inhaled and exhaled, how much carbon fixed during the process! The writer gives some measurements of an ordinary plant, the Abies nordmanniana, a species of silver-fir, which will give a good idea of the rapidity of growth.

The shrub was only two feet six inches in height, and the number of young shoots of this year's growth on it 585. These shoots vary in length from half an inch to six inches, and their aggregate length is 1,171 inches, or nearly 98 feet. Dividing the aggregate of the shoots (1,171 inches)