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SCIENCE 



[N. S. Vol. XXXVIII. No. 979 



agree, however, that chance is nothing but the 

 very thing which emerges to some of us in his 

 X-entity, just some complex of conditioning 

 factors not yet linown. 



Finally, the booli before us is pedagogically 

 nearly ideal, and it may be that its teleologieal 

 philosophy is one of its strong points in this 

 regard. As the author will assuredly agree, 

 scientific research is one thing and the teach- 

 ing of science quite another; the elementary 

 teacher does not try to tell the whole truth, 

 but only those portions which may best lead 

 on to such a state of mind in the student as 

 will some time, perhaps, enable him to under- 

 stand a large portion of the truth. Now, con- 

 sidering that physical causation is far too 

 complex a subject even to be thought about 

 adequately, until the thinking person has ac- 

 cumulated a vast store of accurate scientific 

 experience, it may well follow that a perfectly 

 monistic philosophy would not serve at all in 

 an elementary treatise, and that a somewhat 

 devitalized dualism is the only sort of in- 

 clined plane by which the scientifically un- 

 trained mind may be led toward the highest 

 and clearest altitudes of scientific philosophy. 



In conclusion, the book we have been con- 

 sidering is one of the American ifature 

 Series, is bound in green cloth with a gilt-or- 

 namental back, and is about 4 centimeters 

 thick. It will always be read lying on the 

 table. The paper stock is very heavy, clay- 

 coated and highly surfaced, so that the nu- 

 merous half-tone illustrations are exceedingly 

 satisfactory. It is, however, also true that the 

 position of the book and reader must be prop- 

 erly chosen to avoid dazzling high lights where 

 the midnight lamp is reflected in the mirror- 

 like surface of the paper. As with all such 

 coated papers, a distinct odor of glue is per- 

 ceptible 'throughout the reading; spattered 

 water will play havoc with the pages. 



B. E. Livingston 



Studies in Luminescence. By Edw. L. 

 Nichols and Ernest Meeritt. Published 

 by the Carnegie Institution of Washington, 

 1912. Eoyal 8vo, vi + 225 pp. 



The memoir represents the results of inves- 

 tigation extending over a period of nine years. 

 In large part it gives the experimental obser- 

 vations made by the authors ; but in it are also 

 observations on one or another phase of the 

 general subject, made by other observers, 

 mainly, however, under the guidance of the 

 authors. The work has been aided by occa- 

 sional grants of money from the Carnegie 

 Institution of Washington, and the memoir is 

 published by the institution. The material has 

 been published previously in separate articles, 

 most of which have appeared in the Physical 

 Review; but it has now been given such con- 

 tinuity of form and (in the last two chapters 

 of the memoir) such valuable theoretical dis- 

 cussion as to make the present publication one 

 of unusual interest and value. 



The authors, during these years, have evi- 

 dently kept steadily before themselves the 

 intention of using the spectrophotometer to 

 the farthest possible extent. The success with 

 which they have held to such intention, in in- 

 vestigations of a dozen or so of luminescent 

 substances, is nothing short of remarkable. 

 Measurements of intensities have been carried 

 out far toward the edges of fluorescent and 

 phosphorescent bands. In the cases of nearly 

 all substances investigated, measurements were 

 made to determine the exact form and extent 

 of absorption bands corresponding to given 

 luminescence bands. The dependence of the 

 intensities of luminescence upon the wave- 

 length of exciting light, and the distribution 

 of intensities for some substances when excited 

 by Eontgen rays and by cathode rays, have 

 been studied. More remarkable still is the ex- 

 tent to which the spectrophotometer has been 

 used in following the decay of phosphorescence 

 at various wave-lengths in chosen bands. 

 When one considers how weak the illumina- 

 tions in the comparison fields of this instru- 

 ment are, at the limits of a band or after some 

 time of decay, the range of application which 

 the method finds is surprising. Numerous set- 

 tings were made with intensities in the com- 

 parison fields so small as to convey to the 

 observer no sensation of color. The concord- 



