Page:Popular Science Monthly Volume 49.djvu/737

Rh Hollows in the perpendicular wall faces of the building are preferred, but any proximity to the roof, where cats are liable to abound, is shunned. The nooks furnished in old houses advertised for sale or demolition, by the frames which are set upon them for bill posting, are much resorted to by the birds. The spaces between the frames and the walls are commodious nesting places. The under concavities of corrugated iron roofing furnish hundreds of ready-made tunnels under the cross beams, and when one of these roofs is built in a neighborhood, the sparrows will desert their old, now less attractive quarters "to a bird." "No cat can climb it or stretch a claw far enough up to hook out the nest." The London sparrow is intensely local. "He moves as seldom as he can from his own particular block of houses or square or terrace; and in the suburbs he keeps not only to his own house, but often to the back or front of the house only, not caring to circumnavigate his own suburban garden. In spring, when pulling crocus flowers to pieces becomes a mania with sparrows for a few days, it has been noticed that in many instances all the sparrows in the front of the house will take a fit of crocus-spoiling, while the flowers behind the house are let alone. Or the reverse may be the case, all those behind the house being spoiled, while the sparrows haunting the front of the house and front garden are occupied in some other sphere of activity. If an old nesting place is destroyed, the local birds at once seek another as close as possible to it."

Camphor.—Owing to the widespread use of camphor in the arts and in medicine, its increasing scarcity and expensiveness have raised the problem of artificial cultivation. There are a number of trees, many of them widely separated in genus, order, or species, from which camphor is obtained. The tree, however, which produces most of the camphor of commerce is the Cinnamomum camphora, a member of the laurel family, belonging to the same genus as the cinnamon tree. This tree attains enormous size. The bulk of the camphor imported into Europe comes from Japan and Formosa, and a small amount from China, although the trees are very abundant in the latter country, and the wood is much used. Every part of the tree is said to be useful, even the fruit being employed in the preparation of tallow. The statement that the large use of smokeless powder is responsible for the high price of camphor is denied by Sir Frederick Abel, who says that, while camphor was much used in the manufacture of smokeless powder in the early days, it was soon shown to have serious practical disadvantages, and its use has been to a large extent discontinued. It is, however, used for the conversion of collodion cotton into celluloid, and, in combination with various ill-smelling compounds, is the basis of most moth powders. In a recently published account of the commercial and scientific value of this tree Dr. E. Grassmann urges the importance of increasing the plantations to the greatest possible extent, and the placing of some restriction on the wanton destruction of the trees.

Evolution of the Storage Battery.—A recent article in the Journal of the Franklin Institute, by Maurice Barnett, on the Evolution of the Storage Battery, gives many interesting historical data. It seems that in 1801 Gauterot, while decomposing salt water electrolytically, noticed that on breaking the circuit he could obtain a current of short duration from the electrodes. A few years later Ritter constructed a pile consisting of disks of copper, separated by pads moistened with saline solution; after passing a strong current through this pile he was able to obtain a current of considerable intensity from the pile itself. This was practically the first storage battery. In 1859 Gaston Planté began a series of researches which led him finally to the elaboration of a practical storage battery. He electrolyzed diluted sulphuric acid with rods of the various metals used successively as electrodes. Lead gave the most promising results, not only on account of its capacity, but also because of the intensity of the discharge. Planté came to the conclusion, in 1859, that lead was the only useful metal, and then proceeded to construct his spiral accumulator, which consisted of two plates placed concentric with each other in dilute sulphuric acid, one plate being lead, the surface of which was peroxidized, the other, metallic lead. He got from this electric couple an E. M. F. of