662 



SCIENCE. 



[N. S. Vol. XVIII. No. 404. 



The chapters on the plain and concave 

 gratings, considering the space given to other 

 parts of the subject, might have been fuller. 

 The next six chapters contain theory and ex- 

 periments on polarized light, the rotation of 

 the plane of polarization, the laws of reflection 

 from transparent and metallic surfaces and 

 the spectrophotometer. 



Two statements seem to be misleading. On 

 page 90 it is stated that ' the slit in a spec- 

 trometer is made infinitely narrow by placing 

 it at an infinite distance by means of a lens.' 

 The meaning, of course, is that the divergence 

 of the rays falling on the prism from one 

 point of the slit is made very small by placing 

 it at the focus of a lens. The angular width 

 of the slit is finite, being equal to the width 

 of the slit divided by the focal length of the 

 lens. Again on page 159 it is stated that 

 ' Ordinary photometers * * * may he used 

 to compare the intensities of the total radia- 

 tions of two sources.' Authors of texts can 

 not be too careful to point out that the 

 luminous part of the radiations are but a 

 small part of the total energy sent out by 

 a source. Indeed, it is to be regretted that 

 the subject of optics is generally viewed in 

 this limited light, that no mention is made 

 of the instruments, bolometers, radiometers, 

 thermoelements, etc., used in measuring 

 the total energy of sources, and no notice 

 taken of the interesting properties of bodies 

 with regard to radiations other than luminous. 



These general criticisms have no large value 

 concerning the speciar purpose for which the 

 book was prepared. As a manual of advanced 

 optics it is admirable. G. F. Hull. 



Daktmodth College. 



SCIENTIFIC JOURNALS AND ARTICLES. 



The October number of The American 

 Journal of Anaiomy contains the following 

 articles : 



Joseph Marshall Flint : ' The Angiology, An- 

 geogenesis, and Organogenesis of the Submaxil- 

 lary Gland.' 



EiCHAEU Mills Peakce: 'The Development of 

 the Islands of Langerhans in the Human Embryo.' 



Robert W. Lovett: 'A Contribution to the 

 Study of the Mechanics of the Spine.' 



J. PL.A.YEA1R McMuRRicii : ' Tile Phylogeny of 

 the Palmar Musculature.' 



Bird-Lore for September-October contains 

 articles on ' The Mystery of the Black-billed 

 Cuckoo,' by Gerald H. Thayer, showing that 

 it is a bird of nocturnal habits ; on ' A North 

 Dakota Slough,' by A. C. Bent; 'A Tragedy 

 in Nature,' by William Brewster ; ' Nesting 

 Habits of Two Flycatchers at Lake Tahoe,' 

 by Anna Head, and on ' How Birds Molt,' by 

 Jonathan Dwight, Jr., one of the best authori- 

 ties on this much-mooted subject. There is 

 the sixth series of portraits of Bird-Lore's 

 advisory councilors and numerous notes, in- 

 cluding an interesting article on ' Mortality 

 among Birds in June,' besides book reviews 

 and the reports of the Audubon Societies. 



The Museums Journal of Great Britain for 

 September contains the address of the presi- 

 dent of the Museums Association, F. A. 

 Bather, delivered at the Aberdeen meeting of 

 the association and devoted mainly to the 

 subject of the better arrangement of art mu- 

 seums. A plea is made for smaller exhibition 

 halls and the display of a comparatively small 

 number of objects amid harmonious surround- 

 ings. Among the notes is announced the 

 coming extension of the British Museum (the 

 older building) at a cost of £200,000, and the 

 coining publication of the first volume of a 

 catalogue of the books, manuscripts and maps 

 in the possession of the British Museum, of 

 natural history. 



SOCIETIES AND ACADEMIES. 

 AMERICAN PHYSICAL SOCIETY. 



The fall meeting of the Physical Society 

 was held at Columbia University on Saturday, 

 October 31. The meeting was well attended 

 and was marked by discussions considerably 

 more extended than have recently been usual 

 at Physical Society meetings. These discus- 

 sions add so greatly to the interest of such 

 gatherings that the further development of 

 this feature of the meetings is much to be 

 desired. 



It was decided to hold the next meeting of 

 the Physical Society in St. Louis during con- 

 vocation week in connection with the Amer- 



