Chemistry and Physics. 325 



6. Text-book of Organic Chemistry ; by Henry Leffmann, 

 A.M., M.D. and Chas. H. La Wall, Ph.D. Pp. 231. Phila- 

 delphia, 1904. (P. Blakiston's Son & Co.)— The work is obvi- 

 ously intended for the use of students of medicine and pharmacy. 

 Throughout the book structural formulas are given, even for such 

 complicated compounds as the purine bodies, cocaine, piperine, 

 camphene, salicin and lecithin. But nowhere is there the slightest 

 suggestion that an accepted structural formula, simple or com- 

 plicated, is the result of a study of reactions. Asymmetric car- 

 bon is referred to and stereochemical formulas printed, but the 

 reason given for the latter is that " as molecules occupy space it 

 is desirable to formulate them on a three-dimensional system." 

 Such treatment is calculated to give an entirely wrong idea of the 

 subject, even though the authors have shown in the main good 

 judgment in selecting the compounds to be treated and have given, 

 usually though not always, the structures commonly accepted by 

 chemists. A student acquires some useful information by study- 

 ing about the occurrence and physical properties of organic com- 

 pounds, he learns more by studying those reactions from which 

 are drawn conclusions as to the structure of typical compounds ; 

 when he has the elementary knowledge he may even learn some- 

 thing about the behavior of complicated compounds by looking 

 at the accepted structural formulas, but such formulas are con- 

 fusing and meaningless to one who has not acquired the elemen- 

 tary knowledge. w. j. c. 



7. Electric Inertia. — Sir Oliver Lodge, in an address before 

 the Institution of Electrical Engineers 1903, calculates the inertia 

 which a small sphere charged with a quantity e of electricity and 

 moving with a velocity u has in virtue of its charge. S. H. Bur- 

 bury shows that the magnetic force assumed by Lodge to arise 

 in space from the motion of the sphere is exact if u is supposed 

 to be constant, and also e the charge on the sphere. It is not, 

 however, exact if u or e vary. 



Burbury also asks whether it would not be safer to apply other 

 limits of integration than those employed by Lodge. The paper 

 is a keen criticism of the generalities of the theory of electric 

 inertia. — Phil. Mag., Feb., 1905, p. 243-250. j. t. 



8. Double Refractions. — Ferdinand Braun shows various 

 methods by means of which artificial double refraction can be 

 produced. A thin bundle of glass wool threads made into a 

 layer l mm thick shows changes in light under crossed nicols in a 

 polarization microscope ; the phenomena can be controlled by 

 immersing the bundle in various oils. The author describes also 

 a method of making stratified dielectrics, which consists in cover- 

 ing glass plates with collodion films, alternating with films of 

 aloe resin (the collodion films are dipped in the resin). Thirty 

 such plates show the Iceland spar cross, and eighty, the ring. 

 Gelatine plates soaked in water until soft, immersed in methyl- 

 alcohol, and built up in a symmetrical orientation, give beau- 

 tiful images, such as are produced by biaxial crystals. The 



