Chemistry and Physics. 73 



(2) The relation between the atomic absorption coefficients of 

 nearly all of the elements from hydrogen to silver (also 

 lead) and the atomic absorption coefficient of copper 

 have been determined at the wave-lengths 0-30, 0-34, 0-36, 

 and 0-38 A. 



(3) On the assumption that the absorption of hydrogen is 

 due exclusively to scattering produced by the electron 

 combined with the positive nucleus, it has been found 

 that the scattering for other elements is due, in all prob- 

 ability, solely to the electrons constituting the outer layer 

 of the respective atoms. On the basis of the relative 

 atomic absorption coefficient of hydrogen, the number of 

 ' ' outer electrons ' ' has been estimated for the lighter ele- 

 ments. 



(4) The atomic absorption coefficient increases for different 

 elements nearly proportionally to the atomic number. 

 This fact, taken in conjunction with the interpretation 

 of the atomic number as the number of electrons asso- 

 ciated with the positive nucleus, makes it possible to 

 determine the distribution of electrons between the inner 

 and outer regions of the atoms. 



(5) The number of outer electrons in the lighter elements 

 seems to be constant for the elements placed in the same 

 vertical column of the periodic table. The distribution 

 of electrons thus appears to be closely connected with the 

 periodicity of the chemical properties of the elements as 

 expressed by this system. — Phil. Mag., 37, 165, 1919. 



h. s. u. 



5. Experimentelle Untersuchungen uber die Beugung elek- 

 tromagnetischer Wellen an einem Schirm mit geradlinigem 

 Rande; by Martin Sjostrom. Pp. vi, 110. Uppsala, 1917 

 (Edv. Berling). — This monograph contains a detailed account 

 of an elaborate experimental investigation of the diffraction of 

 short electric waves at the rectilinear edge of a large plane 

 screen. The theoretical object of the work was to test Maxwell's 

 electromagnetic equations on a special case which is susceptible 

 of rigorous mathematical formulation and which is very exact- 

 ing, if not crucial, with respect to the original equations. The 

 theory of the diffraction field corresponding to a point source 

 and an infinite screen, the straight edge of which is parallel to 

 the direction of vibration of the linear oscillator, has been 

 worked out exactly on the basis of Maxwell's equations by C. W. 

 Oseen. Accordingly Sjostrom designed his apparatus to con- 

 form as closely as possible to Oseen 's hypotheses. By using 

 short electric waves the experimenter was able to explore the 

 complicated parts of the field very close (down to one quarter 

 of a wave-length) to the edge of the screen, a scientific feat which 



