KONINKLIJKE AKADEMIE VAN WETENSCHAPPEN 



TE AMSTERDAM. 



PROCEEDINGS 



VOLUME XX 

 N°. 7. 



President: Prof. H. A. LORENTZ. 

 Secretary: Prof. P. Zeeman. 



(Translated from : "Verslag van de gewone vergaderingen der Wis- en 

 Natuurkundige Afdeeling," Vol. XXV and XXVI). 



CONTENTS. 



H. B. A. BOCKWINKEL: "Some Considerations on Complete Transmutation". (Sixth and Seventh 

 communications). (Communicated by Prof. L E. J. BROUWER), p. 910 and p. 924. 



A. Pannekoek: "The Origin of the Saros". (Communicated by Prof. W. DE SlTTER), p. 943. 



C. DE JONG: "Investigation concerning the precession-constant and the systematic proper motions 

 of the stars." (Communicated by Prof. E. F. VAN DE SANDE Bakhuyzen), p. 956. 



W. A. WiJTHOFF: "A relation between the polytopes of the C,A',-fanii'y-" (Communicated by Prof. 

 J. Cardinaal), p. 966. 



J. J. L. DE Neve: "On the Behaviour of Megakaryocytes in the Spleen of the young Kitten". (Com- 

 municated by Prof. J. BOEKE), p. 971. 



G. DE Bruin : "On the replacement, in amides, of an alkylanilinogroup by an aniline group, by 

 heating with aniline hydrochloride." (Communicated by Prof. P. VAN ROMBURGH), p. 983. 



J. E. VERSCHAFFELT: "The viscosity of liquefied gases. X The viscosity of liquid hydrogen'. (Com- 

 municated by Prof. H. KAMERLINGH Onnes), p. 986. • 



P. G. Cath and H. KAMERLINGH OnneS: "On the measurement of low temperatures. XXVII. 

 Vapour-pressures of hydrogen in the neighbourhood of the boiling point and between the boiling 

 point and the critical temperature", p. 991. 



W. H. Keesom and H. KAMERLINGH OnneS: "The specific heat at low temperatures. IV. Measurements 

 of the specific heat of liquid hydrogen. Preliminary results on the specific heat of solid hydrogen 

 and on the heat of fusion of hydrogen," p. 1000. 



H. C. DelsmaN: "Short history of the head of Vertebrates". (Communicated by Prof. J. BOEKE), p. 1005. 

 (With one plate). 



G. Holst and L. HAMBURGER: "On a method of determining spectral intensities by means of 

 photography". (Communicated by Prof. H. KAMERLINGH ONNES), p. 1021. 



G. HOLST and A. N. KOOPMANS: "On the sparking-potential ol argon-nitrogen mixtures'. (Com- 

 municated by Prof. H. KAMERLINGH ONNES), p. 1025. 



G. HOLST and J. SCHARP DE ViSSER: "The brightness of the black body and the mechanical 

 equivalent of light". (Communicated by Prof. H. KAMERLINGH ONNES), p. 1036. 



L. HAMBURGER: "On the light emission of gases and mixtures of gases by electric discharges". 

 (Communicated by Prof. H. KAMERLINGH OnneSi, p. 1043. (With one platei. 



T. Ehrenfest— AfanasSJEWA: "The definiteness of macroscopic processes and the kinetic theory". 

 (Communicated by Prof. J. P. KUENEN), p. 1049. 



W. A. VersluyS: "On Satellite Points on Curves, Given by the Equations: x at^, y bt'^". (Com- 

 municated by Prof. J. Cardinaal), p. 1054. 



H. van TRIGT: "A contribution to the physiology of the freshwater sponges (Spongillidae)." (Com- 

 municated by Prof. C. A. PEKELHARING), p. 1061. 



G. Nordstrom: "On the mass of a material system according to the gravitation theory of Einstein". 

 (Communicated by Prof. H. A. LORENTZ), p. 1076. 



64 

 Proceedings Royal Acad. Amsterdam. Vol. XX. 



