and sieving. Sand-sized material was further separated ac- 

 cording to specific gravity. The lightest material, consisting 

 of diatom frustules, foraminiferal tests, ostracode tests, and 

 certain other organic remains, was floated off with carbon 

 tetrachloride (specific gravity 1.595). Then, the light minerals 

 were separated from the heavy minerals by flotation using 

 bromoform (specific gravity 2.89). 



Grade- Size Determinations and Sediment Chart . Ninety- 

 five snapper samples were collected by lowering a new type 

 of snapper^ to the bottom from a small winch. Grade-size 

 determinations were made on most of the samples using the 

 code system of Emery and Gould^ and, for greater accuracy, 

 pipette analyses were made on eight of the samples. In the 

 Emery-Gould code system (table I), the mechanical analysis 

 is determined by microscopic inspection of the sample placed 

 on a millimeter grid. The size distribution is expressed 

 by the percentage of each size grade in the order of de- 

 creasing diameter of size grades from left to right. Each 

 digit between and 9 expresses the percentage of material 

 by weight in that grade. For example, the digit 3 means 

 30.0 to 39.9 per cent, or 35.0 plus or minus 5.0 per cent. 

 To differentiate between medium and coarse sand, a reference 

 point further simplifies the system. For instance, the no- 

 tation 12.3210 denotes a sediment containing 10 to 19 per cent 

 gravel (greater than 4 mm.), 20 to 29 per cent coarse sand 

 (1 to 4 mm.), 30 to 39 per cent medium sand (0.25 to 1 mm.), 

 20 to 29 per cent fine sand (0.062 to 0.25 mm.), 10 to 19 per 

 cent silt (0.004 to 0.062 mm.), and less than 10 per cent clay 

 (less than 0.004 mm.). If no gravel or coarse sand is present, 

 the reference point is dropped. For instance, 0630 denotes a 

 silty fine sand. It is desirable to indicate genesis of a sedi- 

 ment as well as grade size, so that if shells make up 25 per 

 cent or more of the sample, the letters Sh follow the bottom 

 notation, 5400 Sh. The letter F is used in this connection if 

 Foraminifera make up 25 per cent or more of the sample, 

 and R is used if the sample is predominately rock, cobbles, 

 or pebbles. The results of these analyses, together with 

 sediment color, consistency and grain shape, are shown in 

 table II. 



TABLE I 

 EMERY-GOULD 

 CODE SYSTEM 



Digit in Code 



Coarse 

 Material 

 Present 



Coarse 



Material 



Not Present 



Grain Size 

 (Diameter in mm) 



Sediment 



Name 



4-64 



Pebbles 



1-4 



Coarse Sand 



0.25-1 



Medium Sand 



0.062-0.25 



Fine Sand 



0.004-0.062 



Silt 



0.004 



Clay 



Sand 



Mud 



