Geology and Natural History. 69 



" With the four substances tested, therefore, the result is nega- 

 tive. If thej^ retain the power of giving out any rays capable of 

 penetrating 0'7 cm of air and 0-00005 cm of aluminium, for 0-009 

 seconds after exposure to the (3- and y-rays from 30 milligrams of 

 radium, these rays must be considerably less intense than those 

 due to a layer of uranium salt whose surface-density is 1 milli- 

 gram per square centimeter." 



12. Handbuch der /Spectroscopies von H. Kayser. Dritter 

 Band. Pp. viii, 604; 3 plates, 94 figures. Leipzig, 1905 (S. 

 Hiezel). — Upon the appearance of the first volume of this work 

 on Spectroscopy by Professor Kayser, a somewhat extended 

 notice was published in this Journal, giving an outline of the 

 whole plan (see vol. x, 464, 1900). Since then the second volume 

 has appeared, followed now by the third. So thorough and 

 exhaustive, however, is the work which the author is doing, that 

 it has been found necessary to enlarge the original plan and 

 devote two volumes instead of one to the subject of absorption, 

 here discussed. The present volume contains the description of 

 methods and of apparatus for the investigation of absorption 

 spectra, a discussion of our present knowledge in regard to the 

 connection between absorption and the constitution of the sub- 

 stance; and, finally, a presentation of the results of observations 

 both for inorganic and artificial organic substances. The remain- 

 der of the subject, reserved for the next volume, includes the dis- 

 cussion of the natural organic coloring materials, both vegetable 

 and animal, and also the phenomena connected with absorption; 

 that is, dispersion, fluorescence and phosphorescence. The devo- 

 tion with which the author has given himself to the subject and 

 the thoroughness of his treatment of the entire subject matter are 

 both noteworthy. In the preparation of the first volume he has 

 had the assistance of Professor W. N. Hartley, of Dublin, who 

 discusses very fully the question of the connection between con- 

 stitution and absorption, where the author regarded himself as 

 not sufficiently informed in reference to the chemical side to 

 enable him to handle it satisfactorily. It needs hardly to be said 

 that this chapter (pp. 144-316) shows the same degree of com- 

 pleteness and careful handling which characterizes the whole 

 work. 



II. Geology and Natukal Histoey. 



1. United States Geological Survey, Charles D. Walcott, 

 Director. — Recent publications by the IL S. Geological Survey 

 include the following : 



Folios: No. 120, Silverton Folio, Colorado. This includes a 

 description of the Silverton Quadrangle by Whitman Cross, 

 Ernest Howe and F. L. Ransome; also geography and general 

 geology of the Quadrangle by Whitman Cross and Ernest 

 Howe. 



No. 121, Waynesburg Folio, Pennsylvania, by Ralph W. 

 Stone. 



