Mechanical Extraction of Fibre 573 



impregnated jute for the insulation of low- 

 voltage cables. Such a use for coir was, he 

 said, apparently satisfactory, for he had been 

 informed of such a cable in the shaft of one 

 of the Dortmund collieries, 400 metres deep, 

 which had been working satisfactorily for over 

 ten years. Nowadays jute is used for worm- 

 ing with insulated conductors, for the bedding 

 between lead covering and armour, and for 

 the protective covering outside the armour. 

 The jute is either tarred or impregnated with 

 an insulating and water-resisting compound. 

 When comparing weights of cables it is 

 necessary to remember that, if jute is used, 

 it may in time become saturated with water 

 and considerably increase in weight. From 

 this point of view, jute is objectionable for 

 shaft cables, especially seeing that at the same 

 time as it becomes heavier it also tends to 

 break down the insulation. It is somewhat 

 strange that jute should be practically the only 

 fibrous material used for cables, because other 

 fibres are available. For example, coir yarn 

 made from the fibres of the coco-nut is a 

 likely material, being practically incompressible 

 and tougher, whilst it also resists the water 

 better than any other vegetable fibre, as is 

 well shown by the fact that the "spring" and 

 " mooring ropes " of ships are frequently made 

 of it. In the loose state it is very much 

 cheaper than jute, and even when plaited, 

 although the plaiting is done by hand, it is 

 also cheaper than manufactured jute. The 



