152 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 19 



A. 



IMPROVED TECHNIQUES FOR OCEAN BOTTOM 



SAMPLING 



By Floyd E. Durham 



The obtaining of invertebrate specimens from the bottom of the San 

 Pedro Channel, California, by the Velero IV involves two operations: 

 (1) bringing to the surface bottom samples, and (2) separating the 

 specimens from the substrate. 



The first operation is effected by a Hayvs^ard Standard orange-peel 

 bucket, w^ith a rated capacity of two cubic feet. The area sampled is 2 3/5 

 square feet. The bucket is modified by a canvas hood over the open 

 structure, to prevent the washing out of the bottom sample as the bucket 

 is hauled up through the water. The hood has twelve four-inch by six- 

 inch oval vents, each bearing a flap on the outside, hinged at the top to 

 allow the escape of air and water as the bucket is lowered and to allow 

 the escape of water as the bucket is raised. Because of the hood, the 

 bucket will bring to the surface almost double its rated capacity of soft 

 mud. The bucket is further modified with a lowering pendant which 

 automatically trips the bucket when it strikes the bottom, and allows its 

 operation on the single 7/16-inch steel cable wound on a variable-speed 

 power winch mounted on the working deck. 



At a selected spot, the open bucket is swung clear of the stern by the 

 pneumatically operated A-frame and lowered, with the winch in high 

 gear, at approximately forty fathoms per minute. A tachometer measures 

 in feet the cable paid out and indicates the depth from which the sample 

 is taken. Hauling on the cable closes the four jaws of the tripped bucket 

 and it is brought to the surface at the same speed as it descended. It is 

 swung onto the deck by the A-frame and the contents of the bucket are 

 dropped into a heavy cylindrical tub with a capacity of 4.46 cubic feet. 

 Particularly when sticky mud is being handled, it is necessary to do some 

 cleaning of the bucket by hand. Fragments remaining in the bucket are 

 washed out as the bucket descends for another grab. 



