110 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



third metallic circuit. This third metallic circuit may contain 

 duplex central office telephonic apparatus and form a connection 

 with a subscriber's line as well. This would give the subscriber the 

 benefit of four conductors. The four trunk lines would be formed 

 into three metallic circuits, and three repeating circuits could be 

 used. In other words, the four wires would admit of four sub- 

 sci ibers at each end of the line using the same wires simultaneously. 



In August, 1885, I communicated my duplex telephone system to 

 Prof. S. P. Thompson, of the Finsbury Technical Institute, London, 

 England, and, through his advice and kind offices, a patent was 

 taken out in Great Britain. An application was also filed at 

 Washington. I submitted my systen) to the American Bell Tele- 

 phone Company in May last, but I have not learned whether it has 

 as yet been put in practical operation. In the meantime two 

 claimants have made their appearance, namely, one J. J. Curry and 

 one J. A. Barrett, the fox-rner an employee of the New England 

 Telephone Company, and the latter an employee of the New York 

 Telegi'aph and Telephone Company, both under the control of the 

 Bell Company. One claims the arrangement of the differentially 

 wound apparatus, and the other the arrangement of the repeating 

 coils. 



I will conclude this paper by giving two extracts from the New 

 York Electrical World bearing upon the subject. The first appeared 

 July 31st, or about two months after my system was submitted to 

 the Bell Telephone Company. It says : — 



" The great expense attending the construction of copper lines for long- 

 distance telephony has naturally led those engaged in solving the long-distance 

 prol)lems to seek means for increasing the capacity of the wires. The steps 

 to be taken are analogous to those adopted in the case of the telegraph, where 

 the duplex and quadruplex have greatly increased the value of the lines. It 

 is not hard to believe the report, therefore, that the American Telephone and 

 Telegraph Company, a description of whose lines between New York and 

 Philadelphia we gave lately, is now undertaking experiments with the object 

 of duplexing its wires, and thus practically doubling their capacity and 

 utility. Several methods of duplexing telephone lines have already been pro- 

 posed and have been the subject of discussion and trial among telephonists, 

 but they have not come into use, in this country at least. The delay has been 

 due probably to a lack of necessary incentive, such as the long-distance 

 service now furnishes. While the difficulties to be overcome in the duplexing 

 of telephone lines are greater than with the telegraph, it is safe to say that 

 satisfactory results will in time be attained. We understand that the work 

 in the present instance is in highly competent hands, and even now gives 

 excellent promise of developments scarcely hoped for." 



The second notice appeai-ed October 2.3rd last, and reads as 



follows : — 



