Page:Popular Science Monthly Volume 54.djvu/882

 of the old flashing and safety matches has been retained, and the sesquisulphide of phosphorus is used instead of the white or red phosphorus of the old matches. The latter substance, besides the indispensable qualities of fixity and resistance to atmospheric influences, has the two important properties of inflaming at 95° C, much nearer the igniting point of white phosphorus (60° C.) than of red (260° C), and being therefore easier to light; and of having a low latent or specific heat. With these properties embodied in the inflammable composition of the head, the new match is expected to be comparatively free from accidental explosions during manufacture and export, to take fire by friction, and to burn steadily and regularly. The expectation has so far been fulfilled. The phosphorus compound has a special odor, in which the sulphur characteristic predominates, but, not boiling under 880° C, does not become offensive in the shops; and the match heads made with it do not emit the phosphorescence which is often exhibited by matches made with white phosphorus. It is only feebly toxic by direct absorption, experiments on guinea pigs indicating that it is only about one tenth as much so as white phosphorus.

Trees as Land Formers.—John Gifford, in a paper presented to the Franklin Institute on Forestry in Relation to Physical Geography and Engineering, mentions as illustrating the way forests counteract certain destructive forces, the mangrove tree as "the great land former which, supplementing the work of the coral polyp, has added to the warm seashore regions of the globe immense areas of land." The trees grow in salt water several feet deep, where their labyrinth of roots and branches collect and hold sediment and flotage. Thus the shore line advances. The seeds, germinating on the plant, the plantlets fall into the water, float away till their roots touch the bottom, and there form the nucleus of new islands and life. The forest constantly improves the soil, provided the latter is not removed or allowed to burn. The roots of trees penetrate to its deeper layers and absorb great quantities of mineral matters, a large percentage of which goes to the leaves, and is ultimately deposited on the surface. "The surface soil is both enriched by these mineral substances and protected by a mulch of humus in varying stages of decomposition. As the lower layers rot, new layers of leaves and twigs are being constantly deposited, so that the forest soil, in the course of time, fairly reeks with nourishing plant food, which seeps out more or less to enrich neighboring soils." The forest is also a soil former. "Even the most tender rootlet, because of its acidity, is able to dissolve its way through certain kinds of rock. This, together with the acids formed in the decomposition of humus, is a potent and speedy agent in the production of soil. The roots of many species of trees have no difficulty whatever in penetrating limestone and in disintegrating rocks of the granitic series. As the rock crumbles, solid inorganic materials are released, which enrich neighboring soils, especially those of the valleys in regions where the forest is relegated to the mountain sides and top, as should be the case in all mountainous regions. In view of the destruction caused by mankind, it is a consoling fact that Nature, although slowly, is gradually improving her waste lands. If not interrupted, the barest rock and the fallowest field, under conditions which may be called unfavorable, will become, in course of time, forest-clad and fertile. The most important function of the forest in relation to the soil, however, is in holding it in place and protecting it from the erosive action of wind and rain."

The Atlantic Slope.—The Atlantic slope of the United States is described in the New Jersey State Geological Survey's report on the Physical Geography of the State as "a fairly distinct geographical province. Its eastern boundary is the sea; its western boundary on the north is the divide between the drainage flowing southeast to the sea and that flowing northeast to the St. Lawrence. Farther south its western limit is the divide between the streams flowing east to the Atlantic and those flowing west to the Ohio and Mississippi Rivers." The line between it and the geographical province next west follows the watershed of the Appalachian system of mountains. It is divided, according to elevations, into several subprovinces, all of which elongate in a direction roughly parallel to the shore. Next to the coast there is