388 NOTICES OF NEW BOOKS. 



In rendering the volume into English the translators have adhered 

 to the literal meaning of Dr. (Ileichen's text. Nothing has been deleted 

 from the original, and any additions thought to be desirable have been 

 incorporated in explanatory footnotes and appendices. 



A short section is devoted to. the theory of the microscope ; but it 

 cannot be said that the subject has been treated adequately. The 

 treatment follows orthodox lines, and the Abbe theory of microscopic 

 vision is the accepted one. The description of optical parts is in relation 

 to a microscope of typically Continental design. Such subjects as dark- 

 ground illumination and ultra-microscopy are also referred to, but the 

 fundamental difference between objects which are illuminated by 

 transmitted light and those which are rendered self-luminous is not in 

 any way dealt with. 



In general, it cannot be said that the portion devoted to the micro- 

 scope adds anything to that already available in Enghsh treatises. 



J. E. B. 



Scattering of Light by Solid Substances. By the Hon. E. J. 

 Strutt, F.R.S., Imperial College, South Kensington. Proceedings 

 of the Royal Society, Series A, 95, 476-79. 



The observations already published on scattering of light by gases 

 and liquids naturally led to an examination of the behaviour of solids 

 in this respect. At the first trial it was found that glass scatters very 

 freely, the scattered light being blue, and in many cases almost com- 

 pletely polarized. The observation is so easy that it must almost 

 certainly have been made before, though no mention is made of it. If 

 a narrow parallel beam, say of 6 mm. diameter, from the condenser of 

 an electric lantern is allowed to traverse the interior of a block of glass, 

 the scattered light along the track will be conspicuous. This is a ready 

 method of demonstrating the scattering by small particles. 



Numerous specimens of plate-glass and optical glass have been 

 examined. These all show the scattering, though they differ among 

 themselves in respect of intensity and completeness of polarization. 

 Further experiments were carried out with quartz and with Iceland 

 spar. It was 'found that yellow quartz and smoky quartz have the 

 property of scattering light very strongly, the colouring matter being 

 evidently distributed in the crystal in the form of small particles 

 analogous to those found in srlass. 



J. E. B. 



Mirrors, Prisms and Lenses. A Text-Book of Geometrical Optics. 

 By James P. C. Southall, Associate Professor of Physics, Columbia 

 University. 579 pp., 247 figs. Published by The Macmillan 

 Company, New York. Price $3.25. 



