the release arm before putting the gear over 

 the side. Gather the chain in several small 

 coils and fasten lightly with sail thread to the 

 bail. This will prevent the chain from fouling 

 the corer during the free fall. The fastening 

 should be light enough to break readily when 

 the release mechanism is tripped at the bottom 

 but strong enough not to part while lowering. 



6-17 Rigging for Lowering. — Suspend the 

 coring assembly over the side. Check to see 

 that the trigger weight and line is hanging 

 properly and not fouled, that the corer is 

 hanging properly from the release mechanism, 

 and that the chain is not fouled on the fins. 

 The assembly is now ready for lowering. 

 Important — now remove the safety pin from the 

 release arm. Lower the assembly to the 

 water's edge and set the meter wheel to zero. 

 Commence lowering. 



6-18 Obtaining the Core. — Lowering should 

 be accomplished as quickly as possible since 

 greatest penetration will occur when free fall 

 conditions are approximated. In order to 

 ascertain when the corer has reached bottom, a 

 deep-water bottom-signaling device, the ball 

 breaker, may be used. This device is described 

 in detail in section 6-56. In shallow waters, a 

 simple spring scale and block may be used, as 

 shown in figure 6-5. The block is placed on 

 the winch wire; the spring end is secured to a 

 rigid part of the ship, such as a rail stanchion. 

 As the corer is lowered the wire exerts a steady 

 pressure on the block and spring. An indica- 

 tion that the bottom has been reached, or the 

 release mechanism tripped, will be observed 

 when tension on the spring is relaxed owing to 

 wire slack. This method is satisfactory in 

 shallow coastal waters and has been used suc- 

 cessfully in depths as great as 3,000 meters. 

 In very deep waters, the weight of the corer is 

 often a small fraction of the total weight of the 

 lowering wire and of variable loads caused by 

 the roll of the ship; hence, no apparent release 

 in tension may be observed when bottom is 

 reached. The instant that the scale indicates 

 the corer is on the bottom the winch must be 

 stopped. Failure to do so will result in laying 

 wire on the bottom, thereby kinking it badly. 



6-19 Retrieving the Core. — When the wiiich 

 has stopped, note the amount of wire out. Com- 

 mence hauling in immediately. Do not increase 

 the winch speed until the coring gear is well 

 clear of the bottom. Caution should be exer- 

 cised when the corer approaches the surface. 

 When bringing the corer aboard, it is important 

 to always keep it in a vertical or near vertical 

 position. Never allow the corer to be inverted 

 as this will damage the sample. 



56 



Figure 6'-.5. A spring .scale dynamometer. 



6-20 Removing the Core Sample and Re- 

 cording the Core Data. — As soon as the corer is 

 brought aboard, measure the length of sediment 

 visible on the outside of the instrument and 

 record this in the Penetration column of the 

 M-sheet. Next, carefully remove the cutting 

 edge and core catcher and insert a rubber 

 stopper into the bottom of the liner or cover the 

 end with a plastic cap. Put any sediment re- 

 tained by the cutting edge and core catcher in 

 a sample jar. Now, holding the corer in a verti- 

 cal position, remove the liner. If the liner is too 

 tight to slip out easily, unscrew the core tube 

 from the mainweight and remove both tube and 

 liner from the mainweight. Then slip the liner 

 free of the core tube. If the liner is not com- 

 pletely filled with sediment, fill the empty por- 

 tion with glass wool. This material does not 

 have absorbent qualities nor will it react 

 chemically with the sample. Packing will 

 prevent disturbance of the sample during storing 

 and shipping. Insert a rubber stopper in the 

 top of the liner or cover with a pastic cap, tape 

 both ends securely, and seal with melted wax. 

 The latter will insure retention of the original 

 water content. Measure the length of the core 

 sample and record this on the M-sheet, along 

 with a description of the core. 



H. O. 607 



