Intelligence and Miscellaneous Articles. 69 



supposing that the structure of tourmaline is necessarily at all like 

 either of them ; but there are generally great analogies between 

 different systems exhibiting the same phenomena, and an illustra- 

 tion gives us a concrete stepping-stone to found our conceptions on 

 during the difficult transit to the abstract. 



The passage of a current through an iron wire is accompanied by 

 the production of a series of magnetic elements round it; and the 

 effect of this has been noticed as causing an apparent change of 

 resistance during changes of the current ; but as there is no want 

 of symmetry in the wire, there is no apparent unilateral conduc- 

 tivity. — Scientific Proceedings of the Royal Dublin Society, Jan. 19th, 

 1880. 



ON A SIMPLE METHOD OF IDENTIFYING A SUBMEEGED TELE- 

 GRAPH-CABLE WITHOUT CUTTING IT. BY W. P. JOHNSTONE, 

 ESQ. 



To the Editors of the Philosophical Magazine and Journal, 



Electrician's Office, Alipore, Calcutta, 

 Gentlemen, 3rd May, 1880. 



In continuation of my letter dated 27th April, 1880, I send you 

 now a Postscript, which kindly publish with the Paper*, and 

 oblige 



Tours faithfully, 



Louis Schwendlee. 



P.S. — The following diagram represents a simple method for 

 communication between the repairing-boat and the shore. 



4 a 



i&4H= 



E r 



w&JWewre^rees^^ 





^ 



The telephone T on the boat is worked as before explained : and 

 the telephone T' on the shore is worked by the currents induced in 

 the copper conductor by the currents sent into the guards from the 



* We were unable to comply with our Correspondent's request, the 

 Postscript having reached us after the issue of the June Number.— Eds. 



