Page:Popular Science Monthly Volume 17.djvu/295

Rh of expanding on cooling, of resisting atmospheric and climatic influences better than marble or bronze, of superior resistance to acids, alkalies, and water, and of being susceptible of a high polish. A polished surface of the metal has been exposed for six months in all weathers without showing any change, and another specimen suffered but little from a month's soaking in aqua regia. By reason of its low melting point it is easily prepared for the mold, and in consequence of its power of expanding it gives a nearly perfect cast. In the gelatine mold it yields an impression before the form of the mold is destroyed, and then, if the gelatine be allowed to remain on the metal till it is cooled, it remodels itself so as to be ready for the next casting. The compound, which is called Spence's metal, after its discoverer, Mr. J. Berger Spence, is useful for castings of all kinds, is better adapted than lead for the joinings of gas-and water-works, is suitable for vessels in which chemical processes not requiring a high temperature are to be conducted, and may be employed for joining railings to stones, for coating the holds of ships, for forming damp-proof shields in the walls of houses, for hermetically sealing bottler, for covering cloths, for preserving fruit and other articles of consumption, and to take the place of metal-lined boxes. For all these, and many other purposes, its cheapness and its general adaptability give it a great advantage, for its cost is calculated as only about one fourth that of lead.

The Electric Light and Vegetation.—Dr. C. W. Siemens has recently conducted experiments for two months on the influence of the electric light on vegetation. He planted the quick-growing seeds of certain common hardy vegetables in pots, and divided these pots into four groups, of which one was kept in the dark, one was exposed to the influence of the electric light only, one to the influence of daylight, and one to the influence of the electric light and daylight in succession. The electric light was applied for six hours each evening, and the plants were left in darkness during the remainder of the night. The plants that were kept entirely in the dark soon died; those exposed to the electric light only, or to daylight only, throve about equally; and those exposed to both daylight and electric light throve better than either. The experiments showed that the electric light is efficacious in producing ehlorophyl in the leaves of plants, and in promoting growth. It also appears from them that an electric light equal to fourteen hundred candles, placed at a distance of a little more than two yards from growing plants, is equal in effect to the average daylight of the English March. Other conclusions, which Dr. Siemens thinks he is justified in drawing from his experiments, are—that plants do not require a daily period of rest, but make increased and vigorous progress if subjected during daytime to sunlight and during the night to the electric light; that the radiation of heat from powerful electric arcs can be made available to counteract the effects of night frost, and is likely to promote the setting and ripening of fruit in the open air; and that, while under the influence of electric light, plants can sustain increased stoveheat without collapsing. The expense of electro-culture, being dependent on the cost of mechanical energy, may be made very moderate where natural sources of such energy, such as waterfalls, are available. The buds of tulips, placed in the full glow of an electric lamp during the lecture in which Dr. Siemens related his experiments, expanded into full bloom in forty minutes. It is said that in India, where the bamboo throws up its shoots at the beginning of the rains, it rarely does so with vigor before the occurrence of a thunderstorm, and that its growth is more rapid as the thunderstorms are heavier.

A Test for Watches.—The corporation of Yale College have established an horological bureau in connection with the Winchester Observatory, for the purpose of encouraging improvement in watchmaking and pursuing researches in whatever may aid in the construction of refined apparatus for the measurement of time. In connection with this object they have provided apartments and made other arrangements for testing the running qualities, as to regularity, etc., of such timepieces as may be submitted for the purpose. Certificates of performance are given to the watches thus tested according to the standard of excellence they show. The apartments include a room of the