252 PLEASANT WAYS IN SCIENCE. 



foil to represent the sheathing,* and to correspond to the 

 capacity of the wire. Each sheet of paper thus prepared 

 may be made to represent precisely a given length of cable, 

 having enough tinfoil on one side to furnish the resistance, 

 and on the other to furnish the capacity. A sufficient 

 number of such sheets would exactly represent the cable, 

 and thus the artificial or non-signalling part of the current 

 would be precisely equivalent to the signalling part, so far 

 as its action on the needle at the transmitting station was 

 concerned. " The new plan was first tried on a working 

 scale," says the Times, " on the line between Marseilles and 

 Bona; but it has since been brought into operation from 

 Marseilles to Malta, from Suez to Aden, and lastly, from 

 Aden to Bombay. On a recent occasion when there was 

 a break-down upon the Indo-European line, the duplex 

 system rendered essential service, and maintained telegraphic 

 communication which would otherwise have been most 

 seriously interfered with." The invention, we may well 

 believe, " cannot fail to be highly profitable to the pro- 

 prietors of submarine cables," or to bring about "before 

 long a material reduction in the cost of messages from 

 places beyond the seas." 



The next marvel of telegraphy to be described is the 

 transmission of actual facsimiles of writings or drawings. So 

 far as strict sequence of subject-matter is concerned, I ought, 

 perhaps, at this point, to show how duplex telegraphy has 

 been surpassed by a recent invention, enabling three or four 

 or more messages to be simultaneously transmitted tele- 

 graphically. But it will be more convenient to consider this 

 wonderful advance after I have described the methods by 

 which facsimiles of handwriting, etc., are transmitted. 



* Not "to represent the gutta-percha," as stated in the Times 

 account of Mr. Muirhead's invention. The gutta-percha corresponds 

 to the insulating material of the artificial circuit ; viz. , the prepared 

 paper through which the current along the tinfoil stiips acu inductively 

 on the coating of tinfoil. 



