LONDON. Royal Society, April 3.—Sir J. J. Thomson, president, in the chair.—Dr. TV R. Merton and Prof. J. W. Nicholson: Note on the intensity decrement in the Balmer series. Twelve members of the Balmer series of hydrogen have been observed in vacuum tubes containing a trace of hydrogen in helium at a pressure of 41 millimetres of mercury. In contrast with the diffuse appearance of the last of these members in pure hydrogen, they were observed in the present instance as sharp, though faint, lines. A quantitative comparison of the intensity distribution in these tubes with that in tubes containing pure hydrogen, water-vapour, and a mixture of hydrogen and helium at low pressure has shown that the visibility of the higher members of the series in the high-pressure tubes is most probably due to the fact that the energy under these conditions is concentrated within narrow limits,of wave-length, instead of being distributed through a broadened line the energy-content of which is, in fact, greater. The observed results seem to be incompatible with the quantum theory of the hydrogen spectrum developed by Bohr.—Prof. E. W. Brown: The determination of the secular accelerations of the moon's longitude from modern observations.—Dr. W. Rosenhain and S. L. Archbutt: The inter-crystalline fracture of metals under prolonged application of stress. The authors' observations have shown that in. a number of metals, including lead, mild steel, and an alloy of aluminium with zinc and copper, the prolonged application of stress will, in certain cases, produce an abnormal type of fracture in which the crystals become separated from one another, instead of being broken or torn across in the normal manner. An exact similarity to this type of fracture is found in the “season cracking” of brass. In the latter case the applied stress is an internal one arising from elastic deformation. The authors base an explanation of this type of fracture on the hypothesis, formerly advanced by one of them and widely accepted among metallurgists, that the constituent crystals of metals are held together by thin layers of an amorphous inter-crvstalline “cement,” the properties of which resemble those of a greatly under-cooled liquid.—Dr. J. R. Airey: Zonal harmonics of high order in terms of Bessel functions.