Chemistry and Physics. 165 



fully worked out and is concise and brief enough for use in a 

 very short course on the subject. Several " improved " methods 

 have been introduced, some of which probably will not be as 

 satisfactory to most teachers as those generally used. The 

 introductory part of the book, comprising nearly half of it, seems 

 to be somewhat overdone in fullness. It is difficult to believe 

 that young pupils should study spectroscopy, including spark- 

 spectra, before beginning qualitative analysis. The introduction 

 of the " dissociation theory of solutions " is a step in the right 

 direction, but the rather elaborate treatment here will certainly 

 be far beyond the comprehension of the beginner who has no 

 knowledge of analytical facts. The table of solubilities, which is 

 also included in the introduction, contains a number of serious 

 errors : for instance, lithium fluoride and phosphate are given as 

 soluble in water. h. l. w. 



7. Die Bedeutung der Phasenlehre ; by Dr. H. W. Bakhuis 

 Roozeboom. 8vo, pp. 29. Leipsic, 1900 ( Wilhelm Engelmann). 

 — This lecture is a most excellent presentation of the Gibbs 

 Phase Rule. Perhaps no one is better qualified to treat this sub- 

 ject than Roozeboom who has done so much experimental work 

 on it. The application of the rule to various cases of equilibrium 

 is taken up in a very clear elementary manner, with sugestions as 

 to its possible future application in geology and physiology. The 

 article is most heartily recommended to those who wish to take 

 up the subject. h. w. f. 



8. On the Visibility of Hydrogen in Air. — Lord Rayleigh 

 has resumed some experiments begun in 1897 on the presence of 

 hydrogen in air, prompted by some late results obtained by M. 

 Gautier who, working by chemical methods, finds that air nor- 

 mally contains about Tir,%Tnr °f hydrogen in addition to variable 

 amounts of hydrocarbons. It appeared important to test these 

 results by spectroscopic analysis and the author relates his experi- 

 ence in endeavoring to get rid of the hydrogen which came from 

 the tubes and the drying materials employed. The visibility of 

 the C line with ordinary air was not perceptibly diminished by 

 the passage of the air over red hot cupric oxide. Lord Rayleigh 

 had previously found that hydrogen introduced into nitrogen 

 could be so far removed that the weight remained unaffected 

 although ro",Djnr °f tne residual hydrogen might be expected to 

 manifest itself. Lord Rayleigh concludes that the experiments 

 of Gautier are not above doubt, since it is not stated whether he 

 properly estimated the gas which might have come from the walls 

 of his apparatus. The paper also contains a method of showing 

 the presence of argon at atmospheric pressure in very small quan- 

 tities of air, and also a method of concentration of helium in the 

 atmosphere. — Phil. Mag., January, 1901, p. 100-105. J. t. 



9. Wireless Telegraphy. — Professor Slaby and Count Arco 

 have lately conducted experiments on communicating with dif- 

 ferent stations at the same time, and believe that they have over- 

 come previous difficulties. They have communicated with two 



