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BELL SYSTEM TECHNICAL JOURNAL 



that paragutta has tensile properties equal to cable gutta percha 

 although its gutta content is substantially lower. 



Compression Properties: The insulated submarine cable conductor 

 commonly known as the core is frequently subjected to uneven com- 

 pression stresses during manufacture, laying and repairing. The 

 insulation must therefore be capable of withstanding these stresses 

 without appreciable deformation. To determine the relative merits 

 of paragutta and gutta percha in this respect their comparative stress- 

 strain characteristics under compression have been measured, using a 

 special compression machine,^ and are shown in Fig. 6. In this test 



125 



200 300 400 500 



ELONGATION -PER CENT 



Fig. 5 — Comparative tensile properties of paragutta and gutta percha at 25° C. 



a steel rod 1.6 cm. in diameter was forced endwise into a sheet of the 

 material .375 cm. in thickness at a rate of about 4 cm. per minute 

 while simultaneously recording the deformation and load. These 

 results show that very little difference exists between these materials 

 in this test, and factory handling of cores confirms the general con- 

 clusion. 



Flexibility: The flexibility of submarine cable insulation is important 

 because the core is subjected to considerable flexing during manu- 



3 Hippensteel, Bell Laboratories Record, S, 153 (1928). 



