Societies and Academies

Abstract

PARIS Academy of Sciences, Aug. 28.—Vice-Admiral Paris in the chair.—The following papers were read:—Theorems relative to couples of segments having a constant length, by M. Chasles.— Sixth note on electrical transmissions through the ground, by M, Du Moncel. Placing two zinc plates in two wells 161 metres apart, one in a farmyard, the other on the border of a wood, and connecting them with wire and galvanometer, he got a strong current. He next made a couple with the two waters, separated by a porous vessel, and got a deflection of 80°, the electrode in the water from the farm well being positive. This water contained some sulphuretted hydrogen and organic matter; the other was pure j neither showed acid or alkaline properties. The action was peculiar to zinc electrodes (at least as regards direction of current). From other experiments he concludes that beyond 336 metres the resistance opposed by the water of a river remains nearly the same, whatever the distance of immersion of the plates; hence this resistance is probably indistinguishable from that of the ground at a distance less than 336 metres. Under the best conditions the resistance of the ground varies from 4 to 5 kilometres of telegraphic wire, and if wells or the like do not intervene in the communications it may sometimes be enormous.—On the periodic comet of djArrest, by M. Leveau. He gives an ephemerides to enable astronomers to observe this small comet on its return in 1877. (It was first observed in 1851, and its period is about 61 years.)—Letter from M. Wolf to M. Le Verrier. M. Weber, at Peckeloh, on April 4 last, at 4.25 P.M., saw a round spot on the sun, which was seen without spot on the morning of that day, and also of the next day, at Peckeloh, Zurich, and Athens.—Observations on the Planet 165; positions of some variable stars, by Mr. Peters.—Stars near the pole star, by M. de Boe. Besides the known companion there are two others much nearer and fainter. He observed them first in 1869 and has this year verified their existence. They are probably subject to varying brightness and rapid movements round the principal star; and they are perhaps best seen with small objectives. —On alcoholic and acetic fermentation of fruits, flowers, and leaves of certain plants, by M. de Luca. Fruits, flowers, and leaves in a limited atmosphere of carbonic acid, hydrogen, or air, or in vacuum, undergo slow fermentation, liberating carbonic acid, nitrogen, and sometimes hydrogen, and forming alcohol and acetic acid, without intervention of any ferment. In a close vessel the phenomena are incomplete, owing to pressure of the developed gas; but, with ordinary pressure maintained, neither sugar nor starch will be found after the development of gas has ceased; in their place are alcohol and acetic acid in abundance. The hydrogen liberated is doubtless from decomposition of mannite, which is a sugar with excess of hydrogen.—Influence of pine forests on the quantity of rain which a country receives on the hygrometric state of the air and on the state of the soil, by M. Fautrat. Comparing the rain-fall for fourteen months on a pine forest and a sandy plain 300 metres off, he finds a difference of 83 mm. in favour of the former, or more than 10 per cent, of the rain-fall on the open ground (the difference was only 5 per cent. in the case of oaks and witch-elms). The annual difference in saturation was (in favour of the air above the pines) tcn-hundredths. Of 757 mm. of water which fell, the forest ground received 471 mm.—M. Faye, in presenting Nos. 39 and 40 of Astronomische Mitiheilungen, made reference to M. Wolfs researches on sun-spots and terrestrial magnetism. The last minimum was in 1867, and as the period is 11½years, we should have looked for a minimum in 1878, instead of which it has occurred between the end of 1875 and beginning of 1876, showing a remarkable anomaly of more than two years. The variations of the needle are shown to follow the sun-spots with singular fidelity.