

Notices i 



especting New Booh 



s. 



i 



Axes of coils 



First 



Second 



Third 



coincident. 



combination. 



combination. 



combination. 



Distance 





Distance 













of 



Mean. 



of 



Mean. 



Anglo. 



Mean. 



Angle. 



Mean. 



planes. 





axes. 











17 



0-625 



88 







88 



o 







8 



O 







10 



77 



0-5 



84 



10 



7 



10 



17 



1-5 



52 



10 



70 



20 



7 



20 



17 



20 



38 



1-5 



57 



30 



6 



30 



16 



2-5 



28 



2-0 



406 



40 



5 



40 



16 



30 



22-5 



2-5 



30-8 



50 



4 



50 



15 



3-5 



17 



3-0 



20 



60 



3 



60 



12 



40 



13-4 



3-5 



10 



65 







70 



9 



45 



10 



4-0 











80 



5 



5-0 



8 











85 

 90 



2 

 



417 



Note. — I may state here that I intend to continue this sub- 

 ject, and, when time permits, to trace some of the curves of 

 equal induction. 



XL VIII. Notices respecting New Books. 



Instructions for testing Telegraph-Lines and the technical Arrangement 

 of Offices. Originally written on behalf of the Government of 

 India, under the Orders of the Director- General of Telegraphs in 

 India. By Lotus Schweistdler. Yol. I. Second Edition, 

 Authorized by H. M. Secretary of State for India in Council. 

 London: Triibner and Co., Ludgate Hill. 1878. (8vo, 

 pp. xii and 239.) 

 r PHE title-page contains sufficient information as to the 

 -*- sanction under which this volume has been composed and 

 published. Its contents may be enumerated as follows. It con- 

 sists of two parts, each subdivided into two sections. The first 

 part treats of " Line- testing Arrangements," its two sections being 

 devoted to a description and an exposition of the mathematical 

 theory of (1) Wheatstone's Bridge, (2) the Differential Galvanometer, 

 considered as means of accurately comparing electrical resistances, 

 and so of testing lines. Tor one of these means, however, the 

 Author has a decided preference : he considers Wheatstone's 

 Bridge " by far the best : it combines simplicity of arrangement 

 with great accuracy and sufficient sensibility through wide ranges." 

 The second part treats of "Line-testing," its two sections being de- 

 voted to (1) Regular Tests, i. e. Conduction Tests and Insulation 

 Tests ; (2) Eault-testing, the faults being those of Conduction, Insu- 

 lation, and Interference of Circuits, or " Disconnections," "Earths," 

 and " Contacts." These sections are supplemented by Appendices, 

 fifteen in number, which form more than a third of the volume ; 



