474 Scientific Intelligence. 



sixteenth edition of this admirable work issued as late as 1895, 

 the author devoted himself untiringly to its improvement, never 

 admitting anything into it without personal verification. It is 

 now fourteen years since the last American edition was pub- 

 lished ; and since then two thoroughly revised German editions 

 have appeared. By a piece of good fortune Professor Wells was 

 induced to undertake the translation . of the book for a new 

 American edition, and good evidence of the accurate and pains- 

 taking care with which he has done his work is to be found 

 throughout its pages. While following the original closely and 

 therefore retaining the general form which has given to this 

 Manual its wide reputation, the translator has been obliged to 

 rewrite a large part of the previous edition and to have the 

 whole work reset. In its present form consequently it represents 

 the most accurate methods and the most recent results in qualita- 

 tive analysis, especially in the chemistry of the rarer elements 

 and the less commonly occurring compounds. No distinction, we 

 notice, is made between the alkaloid termination and that of the 

 glucoside ; morphin and salicin terminating alike in in. The 

 book will be warmly welcomed by American analysts not only 

 for the great excellence of the original but also for the faithful- 

 ness with which it has been put into its English form. g. f. b. 



6. The delay in spark discharges. — ^. Warburg concludes 

 from his researches that in the ordinary spark discharge the air 

 changes from a very good insulator into a relatively good con- 

 ductor. In the delay period there is formed, under the influence 

 of the electrostatic lorce, a very weak invisible electrical current 

 which at the end of the delay period goes over into a. visible 

 spark discharge. The delay period continues a longer or shorter 

 time according to the conditions of the electrode; whether they 

 are moist or dry, whether they are under the influence of radia- 

 tions (ultra-violet radiations— X-ray radiations) or not. — Wied* 

 Ann., No. 11, 1897, pp 385-395. j. T. 



7. Photoelectric relations of Fluorspar and of Selenium. — 

 Shortly after Hertz had discovered that ultra-violet light 

 lowered the spark potential, E. Wiedemann and H. Ebert 

 showed that this working of light was limited to the 

 cathode. In regard to this phenomenon Prof. J. J. 

 Thomson quotes a hypothesis of Helmholtz that different 

 substances may possess the power of attracting electricit}^ 

 with different intensities — for instance, if a metal draws to itself 

 positive electricity stronger than the surrounding dielectric does 

 then the metal strives to charge itself positively. If the conduc- 

 tor is surrounded by air in its normal condition then it cannot 

 charge itself, since no electricity can escape. All of these condi- 

 tions are changed when the conductors are subjected to ultra- 

 violet rays. Then enter the following: 1, separation of metallic 

 particles from the conductors ; 2, chemical changes in the gas in 

 the neighborhood of the conductor, which break up the gas iu 

 such a manner that it can take a charge. According to the above 



