Scientific Serials

Abstract

American Journal of Science, August.—On certain astronomical conditions favourable to glaciation, by G. F. Becker. The elements of the earth's orbit undergo slow variations, some of which affect climate. These are the lime of perihelion, which affects the length of the two great seasons; the eccentricity of the earth's orbit, and the obliquity of the ecliptic. The winter of the period of maximum eccentricity in the rigorous hemisphere would be intensely cold as compared with that of the period of zero eccentricity, but the difference would be most marked in the tropics. The summer would be intensely hot, and also wet. On the whole, the period would be most unfavourable to glacialion; the snowfall being the smallest, and the warm rainfall the largest that can occur with the present obliquity. A difference of 1° 9′, however, in the obliquity would make the area to the north of the Tropic of Capricorn 1,800,000 square miles greater than it is to-day, this area being rather more than the combined areas of the Mediterranean and the Gulf of Mexico. The area of evaporation supplying precipitation to the northern latitudes would thus be increased, and the conditions would be favourable to glaciation. Thus a glacial age would be due to the combination of a low eccentricity and a high obliquity, more than to any other set of circumstances pertaining to the earth's orbit. The epochs of such combinations should be deducible from astronomical data.—Development of the lungs of spiders, by Orville L. Simmons. The connection between Limulus and the Arachnida can only be established by a study of the development of the lungs and tracheæ of spiders. The lungs arise as infoldings upon the posterior surface of the appendages of the second abdominal somite, in the same manner as described by Kingsley for the sills of Limulus. The tracheæ develop from the next pair of limbs. The lung-book condition is the primitive, the tracheæ of the Arachnids being derived from it. No ground is left for those who regard the “Tracheata” as a natural group of the animal kingdom.—The generation of chlorine for laboratory purposes, by F. A. Gooch and D. A. Kreider. Chlorine may be conveniently generated by the action of hot hydrochloric acid in a half-strength solution upon lumps of potassium chlorate. These are placed in the upper chamber of a side-neck test tube constricted in the middle. The tube is fitted with a funnel tube reaching to the bottom, and immersed in a flask filled with hot water. When the acid is at 81° the percentage of chlorine in the gas given off is 84. The chlorine dioxide may be destroyed by passing the gases through a wash bottle containing a saturated solution of MnCl2 in strong hydrochloric acid at 90°, and may be still further eliminated by passing the gas through a hard glass tube filled with asbestos and heated.