320 



Scientific Intelligence. 



quantitative determination by gravimetric, volumetric and elec- 

 trolytic methods. Special attention is given to cases of technical 

 importance, and to a large number of rare elements. The book 

 will be of great value to analytical chemists generally, as it con- 

 tains descriptions of many processes that previously have not 

 been readily accessible, and also gives much excellent advice in 

 regard to the selection of methods. The author does not claim 

 to include every reliable analytical method, as he has generally 

 given preference to those with which he is familiar. It is surpris- 

 ing that the use of the Gooch crucible is not generally recom- 

 mended in this book, for, in advising the use of tared filter papers 

 for many things, and in neglecting the uses of this accurate 

 method of weighing precipitates, the author, in common with 

 most German chemists, is a quarter of a century behind the times. 



H. L. W. 



8. Radiation Law of Dark Bodies. — F. Paschen enters into a 

 discussion of a theoretical law stated by Wien, which is deduced 

 from thermo-dynamical considerations. Paschen's observations 

 were made with prisms of fluor-spar, through which the rays were 

 successively reflected by means of mirrors; and a bolometer was 

 used to detect the heat rays. Wien's law is shown to hold within 

 certain regions, and the analogous law of Planck, is found to hold 

 more generally over the whole region of the observations. An 

 article by Wien in the same number of the Annalen answers a 

 criticism of Planck in regard to the fundamental assumptions of 

 Wien. — Ann. der Physik, No. 2, 1901, pp. 277-298; pp. 422-424. 



J. T. 



9. Unipolar Induction. — Most physical cabinets contain an 

 apparatus to illustrate the rotation of a magnet about a current 

 which is conveyed axially through the magnet. This rotation is 

 generally attributed to unipolar induction. A discussion of the 

 reality of the existence of this inductive action has continued 

 through the past two years. Lecher* maintained that the effect 

 is due to the leading-in wires. E. Hagenbach in a leading 

 article of the Annalen der Physik, maintains that the rotation 

 of the magnet is a true phenomenon and falls under Biot and 

 Savart's law, which states that an infinitely long straight 

 current acts upon a magnetic pole with a force which is pro- 

 portional to the current strength and to the strength of the 

 pole and is inversely proportional to the distance. Laplace 

 proved that a stream element acts upon a magnetic pole with a 

 force which is inversely proportional to the square of the dis- 

 tance, and Biot showed that it is proportional to the sine of the 

 angle which the direction of the current makes with the line con- 

 necting both elements. 



The author enters into a discussion of Ampere's laws, Grass- 

 man's law, and the Biot-Savart law in relation to this experiment. 

 — Ann. der Physik, No. 2, 1901, pp. 233-276. J. t. 



10. Effect of Electricity on Bacteria. — In a lecture delivered at 



* Wied. Ann., lxix, p. 181, 1899. 



