13-i Scientific Intelligence. 



scribed a method of coating aluminium with other metals. The 

 aluminium is first dipped in a solution of caustic potash or soda 

 or hydrochloric acid until bubbles of gas make their appearance 

 on the surface. Then it is dipped in a solution of corrosive sub- 

 limate in order to amalgamate the surface. Afterward it is 

 dipped again in caustic potash till gas is evolved. Then the 

 metal is placed in a solution of the salt of the desired metal. A 

 film of the latter is soon formed and is so strongly adherent, that 

 in the case of gold, silver and copper, the plate can be rolled or 

 polished. The coated aluminium can be soldered with ordinary 

 zinc solder. When a coating of gold or copper is desired, it is 

 best to coat first with silver. j. t. 



6. Modifications of Silver. — H. Lttdke discusses the various 

 methods of depositing silver, and investigates the properties of 

 the films. He concludes: that Lehmann's hypothesis that a thin 

 layer of silicate of soda on glass is concerned electrolytically in 

 the process of silvering on glass — is not true, for mirror silver is 

 separated on mica porcelain quartz, fluorspar-platinum, etc. The 

 electrical resistance of many kinds of mirror silver decreases. 



Mirror silver produced however by reduction with sugar of 

 milk, according to Liebig's method, or according to Martin's 

 process, show no decrease of resistance. Heat, light and chem- 

 ical action can easily change allotropic mirror-silver into other 

 good conducting modifications. Mirror-silver gives with ordi- 

 nary silver, scarcely any difference of electromotive force. Mirror- 

 silver in its original unchanged condition, is similar to colloidal 

 silver. — Ann. der PhysiJc und Chemie, No. 12, 1893, pp. 678-695. 



J. T. 



7. Vorlesungen iiber MaxwelVs Theorie der Elektricitat und des 

 Jjichtes, von Dk. Ltjdwig Boi/tzmann". II Theil, 166 pp. 8vo. 

 Leipzig, 1893 (Johann Ambrosius Earth — Arthur Meiner). — The 

 appearance of the first part of this important work was noticed 

 in this Journal about a year and half ago and the scope of the 

 author's plan was then remarked upon. The present part contains 

 the discussion, from the standpoint of Maxwell's theory, of action 

 at a distance with the special cases of electrostatic distribution 

 and induction. 



Errata, in Prof. Mayer's article of "Researches in Acoustics, Paper No. 9," 

 this Journal Jan., 1864. 



Page 2, line 9 from bottom for the read a. 



Page 3, 10 lines from bottom, for duration or the after-sensation read duration 

 of the after sensation. 



Page 4, line 20 from bottom dele (;). 



Page 7, line 8 from bottom for center, read centers. 



Page 12, line 2 from top for tube, read tubes. 



Page 14, line 4 from top dele end of the. 



Page 21, line 17 from top for dessons, read dessous. 



Page 21, line 1 1 from bottom for dessau. read dessous. 



Page 24, line 7 from top for vibrate, read vitiate. 



