P OP ULAR MIS CELL ANY. 



283 



of expanding on cooling, of resisting atmos- 

 pheric 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 show- 

 ing any change, and another specimen suf- 

 fered 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 expand- 

 ing it gives a nearly perfect cast. In the 

 gelatine mold it yields an impression be- 

 fore the form of the mold is destroyed, 

 and then, if the gelatine be allowedto re- 

 main on the metal till it is cooled, it remod- 

 els 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 con- 

 ducted, 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 calcu- 

 lated as only about one fourth that of lead. 



The Electric Light and Vegetation. Dr. 



C. W. Siemens has recently conducted ex- 

 periments 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 di- 

 vided 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 day- 

 light in succession. The electric light was 

 applied for six hours each evening, and the 

 plants were left in darkness during the re- 

 mainder of the night. The plants that were 

 kept entirely in the dark soon died ; those 

 exposed to the electric light only, or to day- 

 light 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 jus+ified in drawing from his experi- 

 ments, are that plants do not require a 

 daily period of rest, but make increased and 

 vigorous progress if subjected during day- 

 time 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 stove- 

 heat 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 en- 

 ergy, 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, ex- 

 panded 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 Watch e. The corporation 

 of Yale College have established an horologi- 

 cal bureau in connection with the Winches- 

 ter Observatory, for the purpose of encour- 

 aging 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 accord- 

 ing to the standard of excellence they show. 

 The apartments include a room of the ordi- 



