20 HENRY DEANE. 



extends along Pitt-street as far as the Railway Station, and is 

 intended to carry the main telegraph lines clear of the city, as 

 well as the telephone lines connecting the southern portion of 

 the city with the Central Telephone Exchange. The northern 

 branch extends from the General Post Office to the Sydney 

 Exchange at the corner of Pitt and Bridge-streets, and serves this 

 important business centre with telephonic communication. The 

 eastern branch runs via Moore and Castlereagh-streets to the top 

 of King-street, where it will connect with an iron pipe conduit 

 system, which carries it through to the Edgecliffe Post Office. 

 The western branch extends from the General P6st Office, Pitt- 

 street side, along Martin Place, Barrack, Clarence and King- 

 streets. 



The tunnels, which are built of brick, are for the most part five 

 feet six inches high and four feet six inches wide and terminate 

 at the General Post Office in a large vault nine feet three inches 

 high and nine feet wide, extending under the footpath of the Pitt 

 street frontage. This vault is used for arranging the cables so 

 that they may be brought into the cable terminal room in regular 

 and proper order. It is here also that the cables are opened out, 

 tested and prepared for laying. The tunnels are accessible at 

 different points by means of shafts and man holes, covered on the 

 street level with ornamental iron covers perforated so as to act as 

 ventilators. Galvanized iron racks are provided in the tunnels 

 for supporting the cables. 



A considerable quantity of cable has already been laid in the 

 tunnels, and the work is still going on. The cables are of the 

 latest type with paper insulation and arranged for metallic cir- 

 cuits, each containing forty to fifty-two conductors. These con- 

 ductors, which are of copper, No. 22 S.W.G., are each wrapped in 

 chemically dried paper laid on spirally, forming what is termed a 

 core, and each two cores are then laid up in a loose strand and 

 afterwards laid up in groups of four. The whole of the cores are 

 covered with a coating of cold drawn lead, which is protected by 

 means of tarred jute. 



