Notices respecting New Boohs. 370 



Researches in Physical Optics. Part II. Resonance Radiation 

 and Resonance Spectra. By B. W. AVood, LLC, Professor of 

 Experimental Physics, Johns Hopkins University. New York : 

 Columbia University Press, 1919. 184 pp., 10 plates. 



[Publication number eight of the Ernest Kempton Adams 

 fund for Physical Besearch.] 



Part I of this Besearch, published 1913, was devoted to the 

 radiation of electrons. An adequate description in detail of 

 this monumental Besearch in Part II would take up more space 

 of the Magazine than can be spared between the multiplicity of 

 subjects. A mere outline of the scope must suffice for the 

 reader. 



The author is the best known exponent of the experimental 

 side of the Science of Light in Physical Optics, and his contribu- 

 tions to the applications of Theory in recent warfare will it is 

 hoped be allowed to see the light now, for the general benefit of 

 Science. 



Of the whole gamut of the light spectrum only a fraction can 

 be apprehended by the human eye; but the author has succeeded 

 in devising apparatus for picking up an impression of the part 

 beyond the visible rays, and utilising them in operations such as 

 heliograpbic work ; the signals can then be received without 

 attracting outside undesirable attention, as of an enemy. 



We have been hearing much lately of the new Theory of 

 Belativity, as revealed in the Gravitation of Light, so that it is no 

 longer a paradox to say that Light is Heavy. In utilising the 

 dark rays, the author provides a discussion of the Light that is 

 Dark. 



I he Besearch is chiefly a careful description of the delicate 

 apparatus required in the experimental work of the spectroscope. 

 Nothing is recorded that has not been observed directly, and that 

 is capable of being redetermined from a description of the 

 apparatus. No appeal is made to new theories of the aether, and 

 there are no elaborate mathematical developments, founded on 

 conjectural hypothesis ; nothing to spoil the pleasure of the 

 physical experimenter, and to interrupt his manipulative skill 

 and interest. 



A Table of the Contents may be cited to show the scope of the 

 investigations. 



• 1. Plane Grating Spectrographs of Long Focus. 



2. The Besonance Spectra of Iodine. 



3. Besonance Spectra of Iodine. 



4. The Series of Besonance Spectra. 



5. Band and Line Spectra of Iodine. 



6. Zeeman-Effect for Complex Lines of Iodine. 



7. A Photographic Study of the Fluorescence of Iodine 



Vapour. 



8. The Magneto-Optics of Iodine Vapours, 



