Shell-fish industries . Fig. 20. Arcachon, France. Oyster parks with low claywalls. Water is retained in those at the right at the lowtide, that at the left being emptied for FlG. 21. Arcachon. Parks with somewhat higher walls con-taining cases for the growing young. Figures from Pro-fessor Bashford Dean. U. S. F. C. Bulletin. Oyster Culture in Europe and Japan 83 The difficulties that have been enumerated are met byconverting the ground into a series of basins by meansof walls or dikes. These ponds are variable in formand in area, but are usually rectangles of two or threehundred sq
Shell-fish industries . Fig. 20. Arcachon, France. Oyster parks with low claywalls. Water is retained in those at the right at the lowtide, that at the left being emptied for FlG. 21. Arcachon. Parks with somewhat higher walls con-taining cases for the growing young. Figures from Pro-fessor Bashford Dean. U. S. F. C. Bulletin. Oyster Culture in Europe and Japan 83 The difficulties that have been enumerated are met byconverting the ground into a series of basins by meansof walls or dikes. These ponds are variable in formand in area, but are usually rectangles of two or threehundred square yards. The walls are often simple andinexpensive. Very shallow basins, like those shown inFigure 20, are easily constructed. To form the wall,parallel lines of planks are held in position on edge bymeans of wooden pegs. Parallel lines of stakes are alsosometimes employed, the space between being filled withsoil. If tide currents are strong, stones are used withthe other filling material, in order to give sufficientstrength to the wall. In some localities it has been profit-able to build walls of solid masonry, but this constructionis usually resorted to only when a large a
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