Chemistry and Physics. 471 



-shown that both vanadium and molybdenum are widely dis- 

 tributed in rocks, the former probably present in the silicates of 

 the amphibole or pyroxene group and in the biotites. 



6. Determination of time of vibration of very high notes. — 

 F. Melde reviews the various methods that have been suggested 

 and used for such determinations and divides them into two 

 groups: A, the subjective; B. the objective. Under A fall the 

 determinations carried out by the human ear, such as the 

 comparison of sounds, one of which is used as a standard. 

 Determinations of notes of 6144 vibrations have been made by 

 this method ; for higher notes the method becomes inapplicable. 

 To the subjective method also belongs the difference-tone method, 

 which consists in measuring a third tone by the use of two pri- 

 mary tones. Notes of 8692 vibrations have thus been measured. 

 To the objective method belong the various graphical and photo- 

 graphic methods. In conclusion the author points out the applica- 

 bility of sensitive flames for the measurement of high notes. — 

 Wiecl Ann., No. 4, 1899, pp. 781-793. j. t. 



7. Heat conductivity of different kinds of glass. — A great 

 number of determinations have been made by Focke and by 

 Paalhorn of the thermal conductivity of glass which differ greatly 

 in value. A. Winkelmann endeavors to reconcile the results 

 and concludes that it cannot be decided which determinations are 

 the better. The discrepancies are in part due to the different 

 ranges of temperature employed. The author concludes that it is 

 desirable to investigate further the dependence of the conductivity 

 of glass upon temperature. — Wied. Ann.^o. 4, 1899, pp. 794-802. 



J. T. 



8. Absorption of Electric Waves by different substances. — The 

 recent experiments in wireless telegraphy have excited interest in 

 the question of the electrical opacity of non-metallic substances. 

 E. Brakly and G. Lebon have undertaken a research upon this 

 question. A coherer together with a battery and a bell were 

 placed in a cavity in the substance which was to be investigated. 

 The substances employed were stones, blocks of cement, and 

 boxes of sand. The electric waves were excited by a Rhigi oscil- 

 lator placed outside the substance. It was found that the opacity 

 depends upon the nature of the substance. The transparency is 

 very great in the case of sand and the kind of building stone 

 employed. It was extremely feeble with Portland cement. The 

 opacity increases with the thickness. Humidity clearly increases 

 the opacity. — Comptes Rendus, April 11, 1899, pp. 879-882. 



J. T. 



9. Radiations of Uranium. — H. Becquerel concludes fur- 

 ther study of these radiations by the following conclusions : The 

 radiation of radio-active bodies approaches approximately in 

 character to X-rays more nearly than to ordinary light. The 

 most singular fact connected with these radiations is the spon- 

 taneous emission of such radiations without known cause. If it 

 could be shown that this radiation occurs without the consump- 



