Geology and Mineralogy. 471 



the radio-active emanation into an electric field the greater por- 

 tion condenses on the negative electrode which then becomes 

 temporarily active. According to J. J. Thomson and Ruther- 

 ford the radio-active emanation throws off a negative electron 

 that ionizes the air, resulting in a j^ositive charge which wanders 

 to the cathode. Curie sees in the emanation only a peculiar kind 

 of streaming out of energy, a condition of matter in which pos- 

 sibly a gas is the bearer of the energy. Rutherford attributes 

 the phenomenon to a radio-active gas of the argon group. The 

 radio-activity is the indication of a series of atomic reactions. 

 Out of thorium, for instance, comes ThX, from the latter arises 

 the emanation and this again suffers a sub-atomic chemical change 

 with formation of induced activity. F. von Lerch studies 

 induced activity without regard to any especial hypothesis and 

 sums up his results at the end of his article. One of his conclu- 

 sions is that palladium appears to absorb the emanations. He 

 also concludes that his experiments show the material nature of 

 induced activity. — Ann. der Physik, No. 12, 1903, pp. '745-'766. 



J. T. 



8. Effect of Pressure on Arc Spectra. — J. E. Petavkl and 

 R. S. HuTTOisr find that at about 44 atmospheres a number of 

 iron lines in the ultra-violet above 3800 are very strongly reversed. 

 The absorption due to the presence of iron vapor results in a 

 diminution of intensity toward the violet end of the spectrum, 

 It was found that certain of the lines appear in the vacuum glow 

 spectrum with their characteristic intensity, neighboring lines of 

 almost equal importance in the ordinary arc and self-induction 

 spark have so greatly diminished as to be quite invisible, the 

 effect, therefore, is in no way connected with the actual exposure 

 of the photograph or the intensity of the light. — Phil. Mag.^ 

 November, 1903, pp. 569-577. J. t. 



II. Geology and Minekalogy. 



1. United States Geological Survey, C. D. Walcott, Direc- 

 tor. — Among recent publications of the Geological Survey are 

 the following : 



Watee Supply ard Irrigation Papers, No. 80. The Rela- 

 tion of Rainfall to Run-off ; by George W. Rafter. 102 pp., 23 

 figs. The relation of rainfall to run-off is influenced by many 

 complex factors and no general expression is possible. Rainfall 

 records covering less than 35 years are not reliable, and no satisfac- 

 tory run-off records are at hand. Mr. Rafter undertakes to estab- 

 lish a more rational theory than has heretofore been proposed. 



No. 81. California Hydrography; by Joseph Barlow Lip- 

 piNCOTT. 478 pp., 4 figs. The data covering the water supply 

 of California has been collected from various sources. 



Nos. 82, 83, 84. Progress of Steam Measurements for the Cal- 

 endar year 1902; by F. H. Newell. No. 82 (195 pp.) covers the 

 Northern Atlantic coast and St. Lawrence Drainage ; No. 83 (300 



