Chemistry and Physics. 75 



ever, to the following points. The differential equations and 

 the experimental curves take into account the mutual inter- 

 actions of the belly, the bow, the bridge, and the string of the 

 instrument. Thus the forcing of the bow coupled with the yield- 

 ing of the bridge are subjected to analysis. The wolf -note pitch 

 of the 'cello is given special attention and simultaneous curves 

 are presented showing cyclical alternations in amplitude. The 

 kinematical theory of the motion of bowed strings is discussed, 

 and it is shown that when the bowed point is assumed to divide 

 the string in an irrational ratio, the mode of vibration 

 approaches one or other of certain ideal types which are com- 

 pletely denned by the motion of one, two, or more equal discon- 

 tinuous changes of velocity moving along the string. In the 

 detailed discussion of these ' ' irrational ' ' modes of vibration the 

 remarkable result is obtained that if n, the number of discontinu- 

 ities, be a 'prime integer greater than unity, a two-step zigzag 

 motion is always possible at the bowed point except when this is 

 at or near an end of the string : whereas, if n be not a prime 

 integer, the motion at the bowed point is necessarily of a more 

 complicated type if it lies outside certain sections of the string. 

 Not only is the subject presented in a lucid, rigorous and 

 thorough manner but the reproductions of the photographs of 

 the curves are beautiful from the esthetic as well as from the 

 scientific point of view. h. s. u. 



II. Geology. 



1. United States Geological Survey; George Otis Smith, 

 Director. — Recent publications of the U. S. Geological Survey are 

 noted in the following list (continued from vols. 45, pp. 475, 476 ; 

 47, pp. 141, 142) : 



Topographic Atlas. — Thirty-nine sheets. 



Folios. — No. 208 Colchester-Macomb Folio, Illinois; by 

 Henry Hinds. In cooperation with the Geological Survey of 

 Illinois. Pp. 14, 2 pis. of topography, 2 pis. of areal geology, 14 

 text figs. 



Professional Papers. — No. 104. The genesis of the ores at 

 Tonopah, Nevada; by E. S. Bastin and F. B. Laney. Pp. 50, 

 16 pis., 22 text figs. 



No. 107. Geology and ore deposits of the Tintic mining dis- 

 trict, Utah ; by Waldemar Lindgren and G. F. Loughlin, with 

 a historical review by V. C. Heikes. Pp. 282, 39 pis., 49 text 

 figs. 



No. 109. The Canning River region, northern Alaska; by 

 E. de K. Leffingwell. Pp. 251, 35 pis., 33 text figs. 



No. 110. A Geologic Reconnaissance of the Inyo Range and 

 the eastern slope of the Sierra Nevada, Cal. ; by Adolph Knopf, 



