1118 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1957 



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Fig. 10 — Cellulose acetate fiber showing extensive surface erosion after one 

 year of marine exposure. Original magnification lOOOX. Photo by F. G. Foster. 



hand side of the rod. In this case, the pholads obtained their start in the 

 jute wrapping and then were able to progress into the Lucite. There was s 

 no attack evident on portions of the rod which were not wrapped with 

 jute. Also, it is interesting to note that the jute in this particular case 

 was treated with an impregnant consisting of 50 parts asphalt, 50 parts ■ 

 paraffin and 2 parts zinc naphthenate. Although this mixture was not 

 highly effective as a preservative, it did serve to hold the jute in position i 

 long enough to enable the borers to become established. There has been 

 no evidence of penetration of Lucite rods on which untreated jute was 

 wrapped. Here, apparently, the jute was destroyed by microbiological ' 

 attack or other borers such as limnoria before the pholads could become 

 well established. j 



In this progress report no detailed comparison of the performance of 

 natural fibers, such as jute treated with various preservatives, will be 

 attempted. Results in many cases are still inconclusive. As might be 

 anticipated, however, the jute specimens as a group have suffered much 

 heavier deterioration by borers and microorganisms than the plastics, j 

 elastomers and casting resins. Particularly noteworthy is the fact that j 

 although there is considerable evidence of bacterial attack upon micro- 1 



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