67. How does an oceanographic ship anchor to take observa- 

 tions in the deep ocean? 



Although most oceanographic observations are nnade without anchor- 

 ing, oceanographic ships sometimes anchor in deep water for several 

 hours, days, or weeks to measure subsurface currents or to obtain re- 

 peated observations in one spot. 



The weight of the anchor need not be great, because the weight of 

 cable lying on the bottom may be more than 2 tons. The Navy often 

 uses anchors of 500 or 800 pounds, but Danforth anchors of only 40 

 pounds have been used to anchor in water a mile deep. 



In depths of 3,000 fathoms, wire tapering from 5/8 to 1/2 inch is 

 normally used to lower the anchor. In greater depths, the taper is from 

 3/4 to 3/8 inch. 



Free-fall anchors have been used for rapid anchoring in deep water. 

 For example, in a recent mooring the total elapsed time for planting a 

 4,000-pound anchor at 17,250 feet was 16 minutes. No attempt was 

 made to recover the cable and anchor. Even if a suitable winch had 

 been available, the cost would have exceeded the value of the anchor 

 and cable. 



To prevent a ship from swinging on its mooring, it may be anchored 

 fore and aft or it may tie to a bridle arrangement of three or four 

 anchored buoys. 



Pell, Claiborne (Senator) 



Challenge of the Seven Seas, William Morrow and Company, 1966. 

 Sverdrup, H. U., Martin W. Johnson, and Richard H. Fleming 



The Oceans, Their Physics, Chemistry, and General Biology, 



Prentice-Hall, 1946. 

 U. S. Naval Oceanographic Office 



Instruction Manual for Oceanographic Observations, H. O. Pub. 



No. 607, 1955. 



83 



