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a 12-24 inch diameter core is the core retainer or core catcher to prevent the 

 core from dropping out of the tube. These large diameter cores might help in 

 the interpretation of ocean bottom photographs because of the large area of ocean 

 floor sampled. 



No entirely satisfactory underwater camera has yet been built but indica- 

 tions are that the multiple shot electronic flash cameras under development in 

 several laboratories will soon fill this need. A camera designed by E.M. 

 Thorndike of Lamont Geological Observatory and Queens College has been tested 

 and is very close to an efficient, reliable design. 



The short core attached totthe bottom of the pole supporting the single 

 shot camera often gives invaluable clues for the interpretation of the photo- 

 graphs. With the advent of the multiple shot camera the design of a multiple 

 bottom sampler is required in order that the same information be obtained. 



Professor Ewing and the writer made a study of the destruction of sub- 

 marine cables following the Grand Banks earthquake (Heezen and Ewing, 1952). 

 This study produced indirect evidence on the transportation of sediments on the 

 sea floor by means of a turbidity current. Although such natural experiments 

 are disasters to the cable companies they give us important information about 

 the ocean floor. 



The importance of having adequate winches overshadows the other needs 

 in both urgency and cost of individual installations. There is little point in de- 

 veloping better gear only to be lost on a faulty winch or to be not used because of 

 the prohibitive time taken by a slow winch! Research vessels and naval vessels 

 are accumulating echograms taken along hundreds of thousands of miles of track 

 but because of lack of precision recorders much of this material is of little use. 

 The easiest way to make an advance in submarine topography is to stop this ap- 

 palling waste by the installation of more precise depth recorders on all naval 

 vessels and research vessels. 



DISCUSSION: Jeffery D. Frautschy 



Dr. Dietz has pointed out the importance of satisfactory wire rope oper- 

 ation to successful sampling, but has not dealt in detail with the matter, consid- 

 ering it to be too involved. In the light of the importance of this subject it is 

 felt that a brief discussion is in order. 



Until very recently most oceanographic organizations have used wire 

 rope in the size of 3/32 inch to 3/8 inch having a 7 x 7 or 7 x 19 construction. 

 This is usually listed as "aircraft cord". It consists of seven strands identical 

 in section, each section containing 7 or 19 wires as the case may be. Six of the 

 strands are laid in a helix around the core strand, the direction of rope lay being 

 opposite to the direction of strand lay. It is readily apparent that the six outer 

 strands are longer than the core strand. In the case of most aircraft cord this 

 difference amounts to about 5 percent. 



Examination of a number of lengths of oceanographic wire rope that had 

 been retired from service revealed that in most cases retirement resulted from 

 mechanical damage rather than corrosion. The type of mechanical failure most 

 often observed seems to result from stretching the core strand beyond its elastic 

 limit. Tests were made to determine the behavior characteristic of seven 

 strand cable which results in this excessive loading of the core. 



A test length of 3/l6 inch diameter 7x19 aircraft cord 75 feet in length was 



