shows a similar graph for parallel tube towing over all three locations. 

 The total areas of the two histograms are equal to each other. The shape 

 is siniilar and it is quite clear that the parallel tube device moves the 

 distribution considerably toward smaller h - values. 



For both sets of data the same ship and the same cable were used. The 

 decline in h is around 0. 8 meters as nearly as we can estimate it on 

 such a crude test that is really composed of by-product data from sound 

 velocity studies. The excess and deficiency in tension would be around 

 500 pounds and it would act on average on about 3000 ft. This particular 

 cable would yield a strain in this case of 31.5 in. orO. 80 meters which 

 with fortuitous accuracy predicts our improvement in h 



Besides the minimizing of the depth fluctuation, the parallel tube device 

 offers the probably more important advantage of orientation stability. The 

 two tubes form a perfect platform for mounting, besides velocimeters, 

 arrays of hydrophones or self -operated sources which can thereby be towed 

 and yet have their complete orientation fixed and known. 



In effect a fairly large set of tubes would provide an experimental 

 facility similar to that of a deeply submerged submarine. Characteristics 

 usually sought in a submarine such as steady slow motion, constant orien- 

 tation, sonic and electrical silence are all quite natural with towed tubes. 



REFERENCE 



Lord, N. W. , 1964, The principles and first test of a new device for 

 deep rectilinear towing, Hudson Laboratories of Columbia University 

 Technical Memorandum No. 72. 



67 



