494 
Scheikunde. — Shinkichi Horiba : „Determination of the Vapour 
Pressure of Metallic ArsenicP 
(Aangeboden door de Heeren P. Zeeman en P. Ehbenfest). 
S ü M M A R Y. 
Tlie vapour pressure of the gray modification of arseiiie and its 
liquid state were measured. Froin these data, raolecular heat of 
sublimation, of vaporization and of fusioii were calculated. 
Natuurkunde. — G. Breit: ,,Calculations of the effeciive permea- 
biliti/ and dielectric constant of a powder.” (Suppl. N". 46 van 
de Mededeelingen uit liet Natuurkundig laboratorium te Leiden). 
(Aangeboden door de Heeren H. Kamerlingh Onnes en P. Ehrenfest). 
S U M M A R Y. 
1. The consideration of tlie effeets of tlie dernagnetizing field tbr 
varions models of the powder shows that (o within the first order 
terms the correetion is the same for all models considered and may 
be expressed by the faet that the force on a sphere of the powder 
is eqnal to the force which would be exerted on the material if it 
were moulded into a solid sphere instead of being powdered. 
2. Different models give results differing in the second order 
terms in the dernagnetizing field. 
(Beide Mededeelingen zullen in extenso in de Proceedings Vol. XX V 
verschijnen). 
Voor de boekerij worden ten geschenke aangeboden : 
V. Door den Heer L. E. J. Brouwer een werk van den Heer 
Felix Klein getiteld : „Gesammelte mathematische Ahhandlungen” Bd.H. 
2“. Door den Heer Einthoven : „Onderzoekingen gedaan in het 
Physiologisch Laboratorium der üniversiteii te Leiden”, 2^^^' reeks Dl. 10. 
De vergadering wordt gesloten. 
