136 PARA RUBBER, 



The use of cheap substitutes, and of rubber mixed with various 

 materials for cables, is now becoming a serious matter. The cable 

 maker cannot easily afford to pay 8s. hd. per lb. for the pure material. 



In Ceylon the Telephone and Telegraph sections of the Post Office 

 Department have, according to Mr. Cook, been contemplating the 

 use of the paper and dry air insulation afforded by the so-called Dry 

 Core cables for underground and sub-aqueous extensions, but the 

 local conditions are so peculiar in regard to the soil and the atmos- 

 phere, that the engineers have not made up their minds as to the 

 desirability of the change from vulcanized rubber insulation. 

 Nevertheless, cheap substitutes are being used in cable work in 

 many parts of the world. 



Burgess, as a result of inquiries made during 1905 in Europe, was 

 able to state that land cable carrying telephone wires, and which at 

 one time were insulated with rubber, are now largely insulated with 

 dry paper, and that heavy cables for electric light supply are demand- 

 ing for use in their manufacture less and less rubber every year, its 

 place being taken by papier-mache and cellulose pulp. He attributes 

 this to the high price of raw rubber, and is of the opinion that there 

 will be a great extension of the electrical application of rubber when 

 the price of raw rubber is reduced. 



Guttapercha has been tried both in Ceylon and India, but the 

 concensus of opinion is that for tropical installations it is far inferior 

 to indiarubber. 



tWl^? 



