534 Notices respecting New Boohs. 



and the side tube similarly drawn out and sealed. These 

 two tubes were then allowed to stand for three days. The 

 drawn-out ends were then joined by a piece of india-rubber 

 tubing, previously soaked in melted paraffin, and the ends 

 broken off. 



The contents of the two tubes being thus placed in con- 

 nexion with each other, were allowed to remain so for 24 

 hours. 



No deposition of a solid on the clean sides of either tube 

 was noticed. On passing a current of air through the two 

 tubes the contents were driven out, a white fume being evi- 

 dent, however, only on the mixed gases reaching the outside 

 air, while simultaneously a strong odour of ammonia was 

 perceptible. 



A similarly conducted experiment gave a similar result, so 

 that it seems certain that dried HG1 and dried NH 3 when 

 mixed do not combine. 



Eastbourne College. 



LY. Notices respecting New Books. 



Alternating Currents. By Frederick Bedell, Ph.D., and Albeet 

 C. Ceehore, Ph.D., of Cornell University. (Whittaker and Co.) 



PART I., of 207 pages, is an analytical treatment of the sub- 

 ject, and Part II., of 104 pages, is graphical. 



The book is intended for students and engineers. Self-induc- 

 tion is regarded as constant and nothing is said of mutual induction 

 between circuits. The transformer is not touched upon. Simple 

 harmonic functions of the time are dealt with almost exclusively, 

 but there are two short references to periodic functions in general. 

 In Part II. the same problems are considered in the same order as 

 in Part I. 



The first eleven chapters, of 175 pages, deal with the following 

 problem : — Griven e the electromotive force in a circuit, of re- 

 sistance It, self-induction L, and containing a condenser of capacity 

 C, to find i the current. The solution of this problem for all cases 

 may be given in one page or in a thousand, depending upon the 

 previous knowledge of the reader. The authors of this book seem 

 at some places to assume a considerable amount of mathematical 

 knowledge ; where, as in chapters iii. and v. for example, they dis- 

 cuss very unnecessarily the conditions for ~Pdx-{-Qdy + $dz being 

 a complete differential. At other places, however, the whole 

 working-out of an easy integral is given, seeming to be copied 

 from a beginner's rough note-book. Regarded as exercise-work 

 on the application of the Calculus to alternating current problems, 



