41] 



VOLUMES XLI-L. 



519 



X-ray spectra, de Broglie, 43, 487; 



44, 484- 



— from certain metals, composi- 

 tion, Kaye, 44, 334. 



— indices of refraction, Einstein, 

 48, 471- 



— penetrating power, Rutherford, 

 44, 401. 



— refraction, Barkla, 41, 560. 



— relations between spectra of, 

 Ishiwara, 44, 335- 



— spectra of iodine and tellurium, 

 Siegbahn, 41, 465. 



— wave lengths, Siegbahn, 43, 167. 



Yerkes, Observatory. 

 SERVATORY. 



See OB- 



Young, C. A., Astronomy, 46, 542; 



47, 386. 

 Young, S., Stoichiometry, 46, 689. 



Ziegler, V., Oil Geology, 45, 423. 

 Zinc Industry, Smith, 46, 689. 

 ZOOLOGY. 



Crinoids, Existing, Clark, 41, 150. 



Edrioasteroidea, Bather, 41, 302. 



Zoology, Reese, 47, 452; in 

 America, 1818-1918, Coe, 46, 

 355; Economic, Daugherty, 45, 

 335; Elementary, Hyman, 49, 

 84; Invertebrate, Pratt, 41, 

 150; Practical, Hegner, 41, 150; 

 Vertebrate, Newman, 49, 384. 



— See Animals, Birds, Insects. 



