are other probes in the listing that measure the same parameters. The term 

 cable-connected indicates whether the instrument requires electrical and 

 telemetering cables from a surface or submersible vessel. 



The use of a specific instrument system for site surveys will be dictated 

 by the requirement and scope of the particular seafloor structure. 



Grab and Dredge Samplers 



The equipment for sampling surficial sediment layers and rocks is 

 discussed here and listed in Table B-6. 



Grab Samplers. These are of two types: clam shell and snapper. 

 Most are bottom trigger operated. These are lowered in a cocked, open 

 position, but on contact with the ocean bottom, a lever trips a catch and a 

 powerful spring causes the jaws to snap shut enclosing a sediment sample. 

 These types include the Berge-Ekman dredge, Dietz-LaFond sampler, Emery 

 foot trip (modified Pettersen), and the mud snapper. 



Orange Peel Bucket Dredges. These operate on the same principle as 

 the grab samplers but are mechanically controlled upon retrieval. As tension 

 is placed on the retrieval wire, a pulley arrangement closes the jaws entrapping 

 a sample. A canvas cover is usually used over the top of the mechanism to 

 prevent the sample from being washed out. 



Tubular Sampler. These resemble corers except for the length of the 

 sample. They free-fall into the bottom and the sample is retained in a small 

 plastic tube. 



Scoopfish (Emery-Champion). This type is towed and falls free to the 

 bottom where it digs into the bottom and trips a mechanism which closes a 

 cap and at the same time reverses the sampler which is retrieved vertically 

 with the digging end up. 



Pipe Dredges. These are as the name implies, a large pipe with one 

 end sharpened and the other end closed by a mesh. They are allowed to lie 

 on the ocean bottom and are dragged horizontally to fill the sampling cavity. 



Rock Dredges. These are rectangular boxes made of metal frames 

 with metal mesh and digging teeth. They are dragged along the bottom to 

 break off and recover rocks. Sediment is not retained because the mesh 

 netting is large. The front end is always kept open. 



Biological Dredges. These are the same as the rock dredges except 

 the teeth are smaller and the mesh is finer to retain biological samples such 

 as shrimp, worms, etc. 



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