Page:Popular Science Monthly Volume 17.djvu/148

 manner. In the undyed state it is the most lustrous of all silks, and is very strong. Some of the prints obtained by Mr. Wardle are beautifully suited to wall hangings, curtains, coverlets, and all kinds of furniture-work; and, while the material has not quite the brilliancy of the mulberry silk in its printed state, it has a richer and softer surface than those of cretonnes or challis, while its lasting qualities are superior to those of any other material. It is beginning to be largely used in France for fabrics and trimmings in which extreme fineness is not required.

Fertilization of the Algerian Sahara.—Some remarkable transformations in the character of the Algerian Sahara have been effected by irrigation. Under its operation a soil has been constituted, in which the intertropical plants grow with great vigor. A cultivator at Ouargla received several medals at the Parisian Exposition for plants which he had raised on a soil thus prepared. The stories that have been told of the productiveness of the Sahara tax the imagination. Fertility is not limited to any one point. It is exhibited wherever water has been brought to the surface of the soil. Most of the Saharan valleys and the beds of the subterranean streams have water in abundance, and only a small effort is needed to bring it to the surface. Sahara is not all a desert, but contains many considerable tracts which are already fit for cultivation. The success which has attended the efforts so far made to introduce tillage renders it nearly certain that a like reward may be gained from similar applications of labor in other parts. Henceforth it will be safe to say that the transformation of the Sahara is only a question of time, labor, artesian wells, means of communication, and security.

The Source of Marsh-Odors.—M. T. L. Phipson recently read, in the French Academy of Sciences, an account of the substances which he had succeeded in extracting from fresh-water algæ. They are palmelline, xanthophyll, chlorophyll, and characine. The last substance receives its name from the odor of chara, a well-defined marshy smell which it gives out. It is lighter than water, on the surface of which it forms minute pellicles, but is very sparingly dissolved. It is obtained by first drying the algae in the air, and then covering them again with cold water as in the preparation of palmelline. After eight or ten hours, a thin iridescent layer will appear on the surface of the water. This is the odorous substance in question. The liquid should be decanted into a long, narrow tube, and shaken with a quantity of ether. The ether dissolves the characine, and leaves it after evaporation in the form of a white, greasy, volatile substance, not saponifiable, soluble in alcohol and ether, hardly soluble in water, and having a strong characteristic odor of the marsh, which it communicates to the water. After some days it evaporates from the surface of the water, or disappears by oxidation, and the water loses its marshy odor. This odor, so strongly developed in plants of the genus Chara, is due to this new substance, which is formed by the plant itself during its life, and is not a product of decomposition. Characine is found in all the terrestrial algæ, and in the confervæ.

A Fossil Ferment.—M. Van Tieghem has called attention, in the French Academy of Sciences, to the evidence of the existence of the butyric ferment, bacilus amylobacter, in the coal period, which has been obtained by the microscopic examination of the radicles of conifers that have undergone its action, and are silicified in the phytogenic rocks of Saône-et-Loire. These fossils have been subjected to much study by M. B. Renault, assistant naturalist of the museum. The radicles exhibit precisely the same characteristic marks of alteration as are seen in corresponding radicles of the present epoch, which have been kept under water, and have become the prey of the bacilus. We know that the effect in the latter case is to subject the cellulose of the radicles to the butyric fermentation; and the conclusion is legitimate that the reactions developed in the marshes at the expense of the ligneous matter during the coal period were identical with those from which we observe the same effects now. The importance of these observations will be appreciated by those who are studying the part which causes that are now in operation have played in the geological past.