418 Notices respecting New Books. 



some are devoted to developing the theory on which the discussions 

 in the previous section are based, others to explaining special 

 applications of those sectiors. Thus the first Appendix to the 

 second section of the second part i* devoted to the theory of 

 fin dine the "Resultant Fault," while the second Appendix, on 

 the execution of Regular Tests," lays down general and practical 

 rules for the operation, and gives an account of the routine observed 

 in their execution on the Indian lines. 



Considered as an account of the principles on which the methods 

 are based, the work can hardly be regarded as in all respects 

 satisfactory : if this had been the Author's sole object it might 

 be fairly said that the arrangement is inconvenient and the exposition 

 obscure. For instance, the accounts of Ohm's law and Kirehhoff's 

 corollaries, which are the foundation of the theory of "Wheatstone's 

 Bridge, are the subject of two Appendices ; and the connexion 

 between them and the various parts of the theory laid down in the 

 preceding section is not very clearly made out. In fact, we doubt 

 whether more than a very few readers would actually make it out 

 unless they had recourse to other books. Added to this, it maybe 

 noted that the correction of the proof-sheets does not seem to have 

 been very thoroughly made*. 



This, however, is a matter of comparatively small importance ; 

 for doubtless the work will be quite intelligible to the class of 

 readers for whom it is written, namely those who are practically 

 concerned in working a Telegraphic System. The information on 

 all points in which such readers will be mainly interested seems 

 to be adequate and to be illustrated by a sufficiency of examples, 

 some of which are very striking. For example (p. 183), " On a 

 single line 420 miles in length . . . there occurs imperfect communi- 

 cation due to a partial Earth." From the data the position of the 

 fault is calculated to be about 363 miles distant ; and on examina- 

 tion the wire is found to be off two posts and resting on the ground 

 at 362-i- miles from the testing-station. Again (p. 203) " Between 

 two lines each 300 miles in length occurs a contact : " measurements 

 and calculation give about 56 miles for the distance of the contact ; 

 and accordingly at about the 56th mile a dead snake is found twisted 

 round the wires, " which during the rain caused considerable cross 

 leakage." 



The Author's object in the composition of the work is best stated 

 in his own words : — " During my stay in Europe I have had many 

 opportunities to watch the working of other Telegraph Admi- 

 nistrations, and have been surprised to find how little progress 

 Testing has made. I was always told, ' Yes, we should like to 

 introduce a general system of Testing ; we know its great practical 

 utility ; but show us a system to do it, and which will work satis- 

 factorily.' 



" Here is a book which I believe contains such a system ; and 

 although I am well aware of many defects, 1 know it has done 

 good service in India, and by it the objects in view have been 



* For example, the letters and o are repeatedly printed for 0, 



