Societies and Academies

Abstract

PARIS. Academy of Sciences, August 26.—M. Bouquet de la Grye in the chair.—Remarks by M. Janssen upon some observations of the Perseids from the Observatory at the summit of Mont Blanc.—On the application of the principle of energy to electrodynamic and electromagnetic phenomena, by M. E. Sarrau.—Critical remarks concerning the determination of sex in the Lepidoptera, by M. Alfred Giard. In discussing the results of the experiments of M. C. Flammarion upon the influence of colours in the production of the sexes in Sericara mori, the author points out certain morphological data which modify the interpretation of the experiments considerably. In the opinion of the author, the great error of physiologists in studying questions of this order, as in many others, is in completely neglecting the morphological data, and in considering the animal or vegetable egg as a point o absolute departure, instead of a complex of energies accumulated by the varied conditions of existence or found in the ancestral organism.—On the mode of action of the brakes of automobiles, by M. A. Petot. From the formuke usually employed to express the relation between the inertia and the co-efficient of adherence it can be deduced that it ought to be impossible to stop an electric tramway as rapidly as another vehicle, under similar conditions of speed and adherence. It is shown in the present note that this is an error, due to an inexact interpretation of the function of adherence during the application of the brake.—On the constitution of white light, by M. O. M. Corbino. According to M. Gouy, the different rays constituting the spectrum of white light are sinusoidal and perfectly regular components of one single complex vibration of any form whatever, and hence it follows that these components, their amplitude and phase remaining invariable, can interfere. According to M. Carvallo, the radiations separated by a grating are independent and consequently cannot interfere with each other. According to the author, the production of a system of mobile fringes in a channeled spectrum affords a crucial test of these two views. From these it is concluded that two radiations taken from different points of a continuous spectrum produced by white light are completely independent, and that in consequence it is impossible to consider them as two sinusoidal components of a single complex vibration.—The sexual elements and copulation in Stylorhynchus, by M. Louis Lé;ger.—On a bacterial disease of the potato, by M. G. Delacroix. The disease in question, which is very prevalent in the centre and west of France, is due to a bacterium which appears to be identical with the Bacillus Solanacearum of E. F. Smith. It possesses the same characteristics on cultivation, and the symptoms of the disease observed in the United States on potatoes and tomatoes are similar to those observed in France. The only suggestion that can be put forward as a remedy is a triennial variation in the crops in order to clean the soil, which appears to be the vehicle of the disease, from the pathogenic organisms which it contains—The invasion of streams of water in the department of Herault by Jussiaea grandiftora, and on the growth of this species in France, by M. P. Carles. The growth of this plant in some districts is so great that it forms true aquatic prairies. It has been stated that this plant could not fructify in France, but this is now shown to be inaccurate, since in the month of September on the River Orb the fruit was formed in the shape of capsules about 29 mm. in length, each capsule having five divisions containing about fifteen seeds. It is by these seeds that it multiplies so abundantly.