37 



of the rock, and if more than one fragment was obtained, the 

 similarity in lithologyo Gravel and rock not in place, i.e., 

 that had been transported, generally were determined on the 

 basis of dissimilar lithology, rounded nature of the fragments, 

 and the lack of fresh fractureSo The dredge generally was 

 towed slowly from a region where no rock and/or gravel existed 

 towards regions where bedrock or gravel was believed to be 

 present o At the first indication of striking hard bottom 

 the ship was stopped and the dredge brought aboard. By 

 repeatedly lowering the dredge and approaching the rocky and 

 gravelly areas from different directions, the general boundaries 

 of these areas were determined. Representative samples of bed- 

 rock and gravel were brought back to the laboratory for later 

 study. 



Most snapper samples were obtained in conjunction with 

 hydrographic work so that a grid pattern was not used in 

 collecting bottom sediment. However 5 towards the end of the 

 survey a number of samples were collected from sparsely sampled 

 areas o Material gathered by a snapper or the Hayward grab 

 were briefly described and placed in air-tight glass jars for 

 later physical and chemical studies in the laboratory. 



Cores of bay sediment were split, briefly described 

 noting especially changes in texture, and placed in jars and 

 brought back to the laboratory for studies similar to surface 

 samples. Some problems associated with use of gravity coring 

 instrviments have been discussed by Emery and Dietz (1941). 

 Their discussion of true core lengths versus collected core 

 length is worth notice. 



