OYSTER BOTTOMS OF MISSISSIPPI SOUND, ALA. 9 



Under the biological and economic conditions obtaining in Missis- 

 sippi Sound in 1910-11, the bottom rated as bearing a scattering 

 growth, on which there are more than 75 bushels of marketable 

 oysters per acre, is regarded as the least productive bottom capable 

 of furnisliing a livelihood to the tongers. Some of the very scattering 

 growth may be capable of supporting a fishery for market, but most 

 of it is not. On the other hand, some of the dense growth is of a 

 character to make it practically worthless for market purposes, and 

 while the oysters are abundant enough, the economic conditions are 

 not such as to warrant tonging. 



The barren bottom, which constitutes by far the greater part of 

 the area covered by the survey, was examined principally with respect 

 to the character, stability, and fixity of its constituent materials. 

 This part of the investigation was more thorough and accurate than 

 in any previously conducted, principally through the use of a mud- 

 sounding machine devised by the writer several years ago. In 

 previous surveys the character of the bottom has been determined 

 by the indications of the sounding lead and pole, which are largely 

 matters of opinion and will not correspond with any accuracy in the 

 hands of different persons. To overcome this difficulty the Bureau 

 now employs the instrument figured on next page. It consists of a 

 large annular bottom (P), from which rises a tripod (T, T) supporting 

 two castings (C and C). Passing freely through shaped orifices in 

 the castings is a steel rod (R) 46 i inches long, provided with a rack 

 and a plunger head (H) 3 inches long and J inch in diameter. Linked 

 to the underside of the lower casting is a pawl (X) connected to the 

 sliding weight (W), which, when at rest, engages with the rack in 

 such manner as to prevent the fall of the rod. 



To use the instrument, a pole of sufficient length is inserted in the 

 eyes at the side of the castings. The rod is raised as far as it will go 

 and is automatically locked in position by the rack and pawl. The 

 instrument is then lowered until it rests on the bottom and the rod is 

 released by pulling on a line attached to an eye at the upper end of 

 the weight. As the plunger always falls through the same distance, 

 it strikes the bottom with a uniform impact, and the depth of its 

 penetration is a comparative measure of the consistency of the 

 bottom. 



In practice, the instrument is used from an anchored boat, and to 

 secure a representative reading from 6 to 10 tests are made close 

 together. Any markedly aberrant readings are eliminated, on the 

 assumption that the plunger has either come into contact with an 

 accidental obstruction, such as a shell, or has fallen into a crabhole 

 or other minor cavity. The average of the remaining depths of 

 penetration, read off in inches in a scale stamped on the rod, is 



