NO. 1 HARTMAN: QUANTITATIVE SURVEY 153 



The tub with the bottom sample is then moved by the four strong 

 handles, and as many men, over to the screens. The surface of the sample 

 in the tub is smoothed, if necessary, and the volume is determined by a 

 calibrated measuring stick. Two small one-half ± pint labelled samples 

 are removed for special studies in sedimentation and foraminifera. 



The second operation, that of separating the biological specimen! 

 from the substrate, is done in a mechanical shaker with a set of graded 

 screens. The process of softening and removing the wastes is accelerated 

 by a spray of salt water from a system of six sprinkler heads mounted 

 above the screens. The top screen, in which the bottom sample is placed 

 by hand-scoops, is of one-half inch diamond mesh, flat, galvanized steel. 

 The second screen, of brass, is twelve mesh per inch, and the third and 

 last screen, also of brass, is twenty-four mesh per inch. The latter deter- 

 mines the minimum size of specimens saved, except for those contained 

 in the two above-mentioned unsorted samples. 



When all the substrate possible has been washed over the side of the 

 ship, the specimens, with the remaining debris, are collected in jars. The 

 larger specimens are removed from the screens by forceps, whereas smaller 

 ones are either gently swept to one corner of the screen with a stream of 

 water and picked up with a spatula, or the screen is inverted over a 

 framed, shallow, white, oilcloth tray. In the latter method, the specimens 

 are dislodged from the screen by tapping it gently and/or applying a 

 draft of air from the exhaust end of a vacuum cleaner head. The speci- 

 mens are then easily crowded to the center of the sagging cloth and 

 scooped up with a large spoon. Preservative, together with a label bear- 

 ing the station number, is added to each jar of specimens. All apparatus 

 is hosed clean prior to the collecting of the next bottom sample. 



The screens are two feet by four feet and are framed with two inch 

 by one inch galvanized channel iron with welded corners. Supporting the 

 screening is one-half inch strap iron on edge every twelve inches. The 

 sieves are inserted into the carrier from the side, and held by a self- 

 locking hasp at each end of the carrier. Longitudinal motion within the 

 carrier is prevented by tightening a winged set screw at the end of each 

 screen. The carrier is well braced and is mounted on four small, steel 

 wheels on a short track, making possible a rapid to and fro motion, power 

 being supplied by a small electric motor directly through an adjustable 

 eccentric (7/16 inch stroke being satisfactory for the work). The four 

 screens and the carrier assembly are mounted on a steel stand supporting 

 the track for the carrier, the mounting for the electric motor, a rack for 

 specimen trays and tools, and supports for the sprinkler heads. 



