320 Scientific Intelligence. 



values expressing the relation between the ionization by cathode 

 rays in different gases (oxygen, nitrogen, etc.) compared with 

 that of air (=1) was found to be approximately the same as 

 those observed for Rontgen rays, except in the case of hydrogen. 

 — Proc. Boy. Soc, No. 431, p. 375. 



3. Kleiner Leitfaden der Praktischen Physik von Feiedbich 

 Kohleausch. Pp. xix, 260 ; 8vo. Leipzig, 1900 (B. G. Teubner). 

 — The many excellent features of the work on Practical Physics 

 by Dr. Kohlrausch, now before the public for some twenty-five 

 years and in its eighth edition, are well known. The same 

 author has now prepared an elementary volume on the same 

 lines, which is designed especially for beginners in Physics and 

 which has a unity character impossible in the larger work. His long 

 experience has enabled him to write a book eminently fitted to 

 fill the place for which it is designed; it is indeed a model both 

 in arrangement and in clearness of statement and conciseness of 

 presentation. It should have a wide sphere of usefulness not 

 only at home, but wherever laboratory work in physics is car- 

 ried on. 



4. Photometrical Measurements and Manual for the General 

 Practice of Photometry with special reference to the Photometry 

 of Arc and Incandescent Lamps • by Wilbur M. Stine, Swarth- 

 more College. Pp. vii, 270. New York, 1900 (The Macmillan 

 Company). — The introduction of new forms of illumination in 

 recent years has much increased the importance of photometrical 

 measurements and extended the range of their application. 

 Hence the value of the present volume, which gives in compact 

 form the physical basis of photometry, the various forms of 

 photometers, the light standards in use and finally the particu- 

 lar application of photometrical measurements to electric lamps 

 of the two types. The author has not only brought together a 

 remarkable amount of material within small compass, but in the 

 frequent and well selected references has practically placed before 

 the reader the important part of the original literature of the 

 subject. 



II. Geology and Mineralogy. 



1. Status of the Mesozoic Florets of the United States. First 

 Paper : The Older Mesozoic ; by Lestee F. Ward, with the 

 collaboration of Wm. M. Fontaine, Atreus Wanner, and F. H. 

 Knowlton. From the Twentieth Annual Report of the U. S. 

 Geological Survey, 1898-99, Part II, General Geology and 

 Palaeontology, pp. 211-748, with 158 jjlates. Washington, 1900. 

 — This extended and timely collaboration brings into convenient 

 form for reference the principal known data concerning the 

 Triassic and Jurassic floras of the United States, including many 

 new descriptions. The salient facts dealt with are here enu- 

 merated. 



The structural determination of several new genera and species 



