CABLE DESIGN AXD MANUFACTURE 195 



cutching process consists of treating the jute with a vegetable compound 

 called catechu or cutch. 



Armor wires were applied over the bedding jute. The use of heavy or 

 intermediate weight near shore has been established by experience with 

 ocean cable. This type of armor is generally employed where the cable 

 may be exposed to wave action, bottom currents, rocks, icebergs, ship's 

 anchors and fishing trawlers. A lighter weight structure having higher 

 tensile armor wires is needed in deep water. Table I shows the essential 

 differences between the armor types employed in the transatlantic cable 

 and the approximate range of depths in application. 



In addition to the above armor types, a shore length of 0.6 nautical 

 mile was provided with an insulated lead sheath under Type A armor to 

 facilitate preferred grounding arrangements and to provide signal to 

 noise improvement. 



Where the tensile strength of the armor wires is most important, as 

 in the type D design, each of the wires was protected against corrosion 

 by a zinc galvanize plus a knitted cotton serving or helically applied 

 tape, the whole assembly being thoroughly saturated with an asphaltum- 

 tar compound. The effectiveness of such protection is clearly apparent 

 Avhen early submarine cables, which used this protection, are recovered 

 and examined. For the heavier armor types, the protection was similar 

 to that of type D, except that the textile serving was replaced by a dip 

 treatment to coat each wire with an asphaltic compound. 



As the armor wires were applied to each type of cable additional pro- 

 tection was obtained by flooding the cable with a special asphaltum-tar 

 compound and then applying two layers of jute yarn over the wires. The 

 jute yarn was impregnated with an asphaltum-tar compound before ap- 

 plication to the cable and then flooded with another asphaltum-tar 

 compound after application. Formulation of cable flooding materials re- 

 quired the use of compounds having a relatively high coefficient of fric- 

 tion to avoid slippage of the cable on the ship's drum during laying. 



To assure satisfactory handling characteristics during the laying op- 

 eration, all of the metallic elements of the cable were applied with a left- 

 hand direction of lay and the lengths of lay (except for the teredo tape) 

 were chosen so that approximately the same helical length of material 

 was used per unit length of cable. Since the teredo tape was relatively 

 soft and ductile compared to that of the other metallic components, it 

 was not necessary to equate its helical length to that of the other com- 

 ponents. Width and lay of the teredo tape were selected to give a smooth, 

 tight covering. 



The choice of direction and length of lay of the jute layers was based 



