392 



SCIENCE 



[N. S. Vol. XLIII. No. 1107 



gardeners and agricultural students," and no 

 doubt fills a, need for a brief popular presenta- 

 tion. However, the diseases selected are on 

 the whole a little raore applicable to English 

 than to American needs, though many of them 

 are among our common troubles. 



Milburn is secretary of agriculture and lec- 

 turer in agriculture, Lancashire County Coun- 

 cil, England, and Bessey is professor of botany 

 in our own Michigan Agricultiiral College. 

 The latter's connection with the work has been 

 largely confined to a prefatory note and a little 

 of the subject-matter, especially in the intro- 

 ductory chapter dealing with the nature and 

 classification of fungi and with fungicides. 

 Bessey's connection with this book makes it 

 the fifth on plant diseases that has been put 

 forth by American authors in recent years, 

 and we understand that a revision of one of 

 these and a new one are now in preparation, 

 showing the growing importance of vegetable 

 pathology in this country. All of the books 

 presented so far or under consideration are 

 by men who have devoted more of their time to 

 teaching than to the experimental side of plant 

 pathology, especially as regards prevention of 

 disease. The next author of a book on plant 

 diseases should come from the latter class. 

 Q. P. Clinton 



PROCEEDINGS OF THE NATIONAL 

 ACADEMY OF SCIENCES 



The second nimaber of Volume 2 of the 

 Proceedings of the National Academy of Sci- 

 ences contains the following articles : 



1. Personal Equation and Steadiness of Judg- 

 ment in the Estimation of the Number of 

 Oijects in Moderately Large Samples: J. 

 Aethur Harris, Station for Experimental 

 Evolution, Cold Spring Harbor, IST. Y. 

 "While there is no certain differentiation 



among the experimenters in personal equation, 

 they differ distinctly in steadiness of judg- 

 ment. The latter is conspicuous in contrast 

 with the former in that it is unmistakably 

 influenced by previous experience. 



2. Polypeptide-Hydantoins: Treat B. John- 

 son, Sheffield Scientific School, Yale Uni- 

 versity. 



The formulas for a large number of poly- 

 peptide-hydantoins are set up. Some of these 

 substances have already been synthesized and 

 methods for synthesizing others are being 

 developed. 



3. Recent Explorations in the Cactus Deserts 

 of South America: J. 'N. Hose, Division of 

 Plants, TJ. S. ISTational Museum, Washing- 

 ton. 



Large collections of cacti in South America 

 have been made, including many species which 

 have never before been collected and some 

 which, though collected, have been poorly de- 

 scribed or wrongly classified. 



4. On the Albedo of the Planets and Their 

 Satellites: Henry ]N"orris Eussell. 



A table is given of the values finally derived 

 for the albedo of the various planets and 

 satellites. The values are in agreement with 

 the current views of the constitution of the 

 bodies. The value for the earth is intermedi- 

 ate between those of cloudy and cloudless 

 planets. 



5. Quantum Relations in Photo-Electric Phe- 

 nomena: E. A. MiLLiKAN, Eyerson Physical 

 Laboratory, University of Chicago. 



So far as experiment has thus far gone 

 Einstein's equation seems to be an exact state- 

 ment of the energies of emission of corpuscles 

 tmder the influence of light waves. Thus the 

 correctness of the quantum theory and the 

 reality of Planck's h are corroborated. 



6. The Chemical Activity of the Ions of 

 Hydrochloric Acid Determined by Electro- 

 motive Force Measurements: James H. 

 Ellis, Eesearch Laboratory of Physical 

 Chemistry, Massachusetts Institute of Tech- 



In this paper are presented accurate meas- 

 urements of the electromotive force at 18, 25 

 and 35° of voltaic cells of the type H,, HCl, 

 Hg„Cl. -\- Hg, with the acid-concentration 

 varying from 0.03^.5 normal. From the data 

 are calculated the energy effects attending the 

 reaction which takes place in such cells and 

 those attending the transfer of hydrochloric 

 acid in aqueous solution from one concentra- 

 tion to another. From these results are then 

 calculated the chemical activities (or effective 



