TKANSACTIONS OF SECTION G. 769 



proves that to maintain easy conversation when the trunk wires are extended to 

 local points it is only necessary that the local lines shall be of a standard not lower 

 than that of the trunk line. The experiments also confirm the conclusion that 

 long distance speaking- is solely a question of the circuit and its environments, and 

 not one of apparatus. The instruments finally selected for actual work were 

 Gower-Bell for Loudon and Roulez for Paris. 



3. The results are certainly most satisfactory. There is no circuit in or out of 

 London on which speech is more perfect than it is between London and Paris. 

 In fact, it is better than I anticipated, and better than calculation led me to ex- 

 pect. Speech has been possible not only to Paris but through Paris to Bruxelles, 

 and even, with difhculty, through Paris" to Marseilles, a distance of over 900 miles. 

 The wires between Paris and Marseilles are massive copper wires specially erected 

 for telephone business between those important places. 



4. Business Done. — The charge for a conversation between London and Paris 

 is 8s. for three minutes' complete use of the wire. The demand for the wire is 

 very considerable. The average number of talks per day, exclusive of Sunday, ia 

 eighty-six. The maximum has been 108. We have had" as many calls as nineteen 

 per hour — the average is fifteen during the busy hours of the day. As an instance 

 of what can be done, 150 words per minute have been dictated in Paris and trans- 

 cribed in London by shorthand writing. Thus in three minutes 450 words were 

 recorded, which at 8*. cost fi ve words for a penny. 



5. The difficulties met with in long distance speaking are several, and they 

 may be divided into {a) those due to external disturbances and (6) those due to 

 internal opposition. 



0. The paper enters fully into the technical details by which these difficulties 

 have been surmounted. 



1 . Lightning. — A metallic telephone circuit may have a static charge induce! 

 upon it by a thunder cloud. Such a charge is an electric strain which is released 

 when the charged cloud flashes into the earth or into a neighbouring cloud. If 

 there be electro-magnetic inertia present the charge will surge backward and 

 forward through the circuit until it dies out. If there be no E.M.F. present it 

 will cease suddenly, and neutrality will be attained at once. Telephone circuits 

 indicate this operation by peculiar and characteristic sounds. An iron wire circuit 

 produces a long swish or loud sigh, but a copper wire circuit like the Paris-London 

 telephone emits a short, sharp report, like the crack of a pistol, which is sometimes 

 startling, and has created fear, but there is no danger or liability to shock. Indeed, 

 the start has more than once thrown the listener off his stool, and has led to the 

 belief that he was knocked down by lightning. 



8. The future of telephone working, especially in large cities, is one of under- 

 ground wires, and the way to get over the difficulties of this kind of work is per- 

 fectly clear. We must have metallic circuits, twisted wires, low resistance, and 

 low capacity. In Paris, a remarkable cable, made by Fortin-IIerman, gives an 

 exceedingly low capacity, viz. only -OGO ^ per mile. In the United States they 

 are using a wire insulated with paper which gives -08 ^ per mile. We are using 

 in London Fowler-Waring cable giving a capacity of 1-8 per mile, the capacity 

 of gutta-covered wire being 3 per mile. 



2. On the Teleplwning of Oreat Cities. By A. R. Bennett, M.I.E.E. 



The paper discusses how the extensive demand for Telephonic Exchange com- 

 munication, which in the course of a few more years is certain to arise in all large 

 cities — a demand of which no conception can be formed from the present condition 

 of Telephone Exchanges in this country— can be met and satisfied. Given low rates 

 and a fairly efficient service, the time will come, and that at no distant day, v;hen 

 every shopkeeper, and almost every householder, will look upon a Telephone 

 Exchange connection as as much of a necessity as gas or water. Indications are 

 not wanting even now_ of what may be expected when the inhabitants of large 

 towns come to realise what an important business and social auxiliary a 

 properly conducted Telephone Exchange is, for in Galashiels and some other 



1891. 31, 



