300 The Philippine Journal of Science i9i8 



tween the tensile strength of coir obtained from husks from 

 which copra has been made and that of coir obtained from 

 slightly immature nuts, so highly recommended. While it is 

 evident that the machine-cleaned filaments from Laguna husks 

 possess a higher average tensile strength than the retted fila- 

 ments from Ilocos Sur, no definite conclusions can be drawn as 

 to the cause of the difference. It may be due to any of a number 

 of causes ; such as a difference in the age of the husk, the action 

 of salt water on the retted fiber, the variety of the coconuts, the 

 nature of the soil upon which the nuts were grown, climatic 

 conditions, etc. 



Elongation. — Perhaps the most characteristic and striking 

 property of coir is its extraordinary elongation when subjected 

 to tension. There is little difference between the retted and 

 machine-cleaned filaments in this respect, the average being 

 about 30 per cent for each kind. Since extensibility is a measure 

 of ductility, the data given in Tables III and IV also show that 

 coir is a highly ductile fiber. 



Burr ** says : 



One of the most important and valuable characteristics of any solid 

 material is its "ductility," or that property by which it is enabled to 

 change its form, beyond the limit of elasticity, before failure takes place. 

 It is measured by the permanent "set," or stretch, in the case of a 

 tensile stress, which the test piece possesses after fracture; also, by the 

 decrease of cross-section which the piece suffers at the place of fracture. 



Unfortunately most writers on coir have erroneously inter- 

 preted high ductility to mean high elasticity. Per se there is no 

 connection between the ductility and the elastic properties of a 

 material, and most writers confuse deformation with elasticity. 



Elasticity. — Before proceeding with the detailed discussion 

 of the elastic properties of coir I desire to quote typical pass- 

 ages from the literature that show the misuse of the term 

 "elasticity" as applied to coir.''* 



Watt ^'^ states : 



The merits of coir as a rope fibre are now fully appreciated throughout 

 the world, the elasticity and lightness of the fibre making it eminently, 

 suited for this purpose. But to these properties has to be added its great 

 power of withstanding moisture even under continued actual submersion. 



^ Burr, Wm. H., The Elasticity and Resistance of the Materials of 

 Engineering. Chapman & Hall Limited, London; John Wiley & Sons, 

 Inc., New York, 6th ed. (1913), 204. 



^ Small capitals are employed to emphasize the words misused. 



"'Watt, Geo., op. cit. 437. 



