Page:Popular Science Monthly Volume 52.djvu/738

718 toward the circumference. This motion is supposed to be caused by the great daily change in temperature, often amounting to 80°, and an unequal upward motion of the mass below, increasing toward the center of the lake. A few patches of shallow earth lying on the pitch and covered with bushes and small trees are scattered over the surface of the lake.

Nature's Landscape Gardening.—A curious and interesting and yet easily explainable phenomenon is mentioned in a recent paper by N. F. Drake, in the Journal of Geology, on The Topography of California. In assisting to map a number of sand-dune areas along the coast in San Luis Obispo County it was noticed that where the sand was free from vegetation or obstruction it was piled in ridges at right angles to the prevailing sea breezes; but that where patches of vegetation grew, the dunes became parallel to the direction of the wind, and where the vegetation became thicker over the ground the regularity of the arrangement of the dunes was more broken. The reversal of the direction of the ridges where patches of vegetation existed was accounted for as follows: A mass of grass or bushes once started would check the sand from moving at that point and make a shelter for deposits to the leeward. This point of the sand dune now being more stable, other plant growth would spring up—mainly on the leeward side, so as to lengthen and increase the elevation of the ridges, while the unprotected sands at either side would drift away, thus forming narrow parallel ridges in the direction of the prevailing winds. Ridges from fifty to seventy-five feet high and four to six hundred feet long, or even longer, were not uncommon where the sand dunes were extensive.

Pegamoid.—Pegamoid is a substance of similar composition with celluloid, possessing its desirable qualities, while it is not inflammable and does not lose shape when heated. It was discovered by an English lithographer seeking a means of protecting the posters of his making from injury by the atmosphere. Its composition is a secret, but it appears to contain a nitrified cellulose, alcohol, and camphor, or the essential constituents of celluloid, together with some substances intended to increase its impermeability and make it supple and uninflammable. It may be applied in thin varnishes to any material—cloth, leather, paper, etc.—so closely that it can not be separated by any mechanical means, and so as to form an impermeable coating, easily cleaned by washing, and proof against heat, grease, and alkalies, while it has the further property of communicating its qualities to the material to which it is applied without destroying its individuality. Pegamoid cloth is a cotton fabric covered with a suitable thickness of pegamoid and gauffered. The process of manufacturing it is very simple, and consists in dyeing the cloth in the desired color, mechanically coating it with colored pegamoid, and stamping it. This is only one of the innumerable applications of which pegamoid is capable.



method of reproduction of the eel, long a puzzle in zoölogy, has been discovered. Young eels were known, but at too advanced a stage of development to give any clew to their primitive or larval state, and no eels in this condition had ever been recognized. Theodore Gill suggested in 1864 that larval eels might be identified with the Leptocephalus, an animal which is found on the British shores, in the Mediterranean, and on the surface of the water in various parts of the world. It has a body several inches in length, thin, and of uniform width, like a piece of ribbon, transparent, and unpigmented. Professor Gill's suggestion was verified by the investigations of Yves Delage in 1886 and Grassi and Calandruccio in 1892 and 1893, who showed that two species of Leptocephalus were larvae respectively of the conger and the common eel. Fuller accounts of the observations of Professors Grassi and Calandruccio have been published recently in the Proceedings of the Royal Society and the Quarterly Journal of Microscopical Sciences. The specimens investigated were captured, along with deep sea fishes, in the Strait of Messina, where the currents are strong and beset with 