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original water content, and to prevent chemical changes accompanying increased 

 bacterial activity. Cores of red clay, for example, shrink as much as 75% on 

 drying, and structures become almost unrecognizable. On our earlier expedi- 

 tions we attempted to retain portions of the sediment chemically unchanged by 

 placing them in sealed mason jars, without addition of water or preservative. 

 Samples treated in this way show little change in water content or chemical prop- 

 erties even after several years, but bedding and other structures are lost. Our 

 present technique is to wrap three-foot sections of the corers in a thin sheet of 

 cellophane or other plastic material, which is held in shape by plastic discs at 

 each end and sealed with scotch tape. This cylinder is then placed in a card- 

 board mailing tube having a rather snug fit. This in turn is enclosed in wrap- 

 ping paper, sealed with tape, and dipped in molten tropic wax. The wrapped 

 core sections should be placed as soon as possible in an ice box at a temperature 

 of about 0° centigrade. We are constructing a core storage room, capable of 

 holding 12,000 feet of cores, which can be kept saturated with water vapor at a 

 temperature just above freezing. 



In addition to bottom samplers, other instruments are needed to determine 

 in situ the properties of the bottom and the sediments, and the processes taking 

 place on or under the bottom. The deep sea lead, the oldest of all oceanograph- 

 ic instruments, is a device for determining bottom properties, as is its lineal 

 descendent, the recording echo-sounder. 



More recent examples of this kind of instrumentation are the bottom 

 temperature gradient probes developed by BuUard, Maxwell, Snodgrass and 

 Isaacs. The type used at the Scripps Institution consists of a hollow steel spear 

 10 feet long and 1.64 inches in outside diameter, in which thermistors are 

 mounted near each end. The spear is attached at its upper end to a water-and 

 pressure-tight chamber, within which is a battery-powered, self-balancing, 

 null-type potentiometric recorder. From a 30-minute continuous record of the 

 temperature difference between the two thermistors it is possible to deduce the 

 undisturbed temperature gradient in the sediments. A core is obtained at the 

 same station, and samples of the sediments are carefully preserved for labora- 

 tory determination of thermal conductivity. The product of the conductivity and 

 the temperature gradient gives the heat flux through the sea floor. The probe and 

 recording assembly are illustrated in the frontispiece. Developments are underway 

 to determine the thermal conductivity in situ as well as the temperature gradient. 



Measurement of variations in the electrical potential between the super- 

 natant water and the sediments, and in the amount and size of colloidal particles 

 suspended in the supernatant water, either by direct sampling or by turlDidity 

 measurements, are examples of the study of sedimentary processes. 



Many attempts have been made to develop sediment traps to measure the 

 present rate and character of deposition. A perfect sediment trap must not in- 

 terfere with the normal processes of sedimentation and yet must be capable of 

 collecting deposited material. The first requirement means that the sediment 

 trap must look to the water and the bottom as if it were not there, the second 

 that it must retain the sedimentary material which reaches it, and these two re- 

 quirenments are so nearly incompatible that no sedimient trap built to date has 

 been more than partly successful. 



