118 NEW SOUTH WALES 



The Royal Commission (Ireland) say, fruitful oyster mud may vary 

 within very wide limits, from almost pure sand to almost plastic clay. 

 In the very sandy grounds, there must however be always a sufficient 

 quantity of highly hydrated clay to render the sand adhesive and to 

 preserve it from becoming a mere loose running mass. 



In the clayey grounds there must always be calcareous mud to make the 

 clay porous and prevent it becoming too hard, — clay marls, with some 

 intermixed sand, being perhaps the best of all materials for oyster grounds. 



The earth known as the London clay appears to be the soil peculiarly 

 adapted for oysters. It may be well here to explain that the term 

 ' London clay' is employed in a general and a special sense. In the 

 former it is used as a collective name for a number of beds of the old 

 tertiary formation, consisting of gravels and sands below and of clays 

 above. In the special or limited sense, it is applied to the bluish or 

 blackish clay, sometimes mixed with a greenish coloured earth and white 

 sand, which forms the upper parts of the beds just mentioned. London 

 clay is plastic clay, not differing much in chemical composition from 

 ordinary potter's clay. All fruitful oyster muds contain organic matter, 

 always due in part to the presence of infusoria, and sometimes in part 

 to small algse or confervse, remains of shell-fish and other marine 

 creatures. 



Berti-am says, one of the most lucrative branches of oyster farming in 

 France is the fattening of oysters in claires, at Marennes, which have 

 been brought from the He de lie breeding pares. In the claires the 

 oysters become green, and of considerably more value than the white 

 oyster. The peculiar colour and taste of the green oyster are imparted 

 to it by the vegetable substances which grow in the claires. The industry 

 carried on at Marennes consists chiefly of the fattening in claires ; and 

 the oysters operated upon were at one period of their lives as white as 

 those which are gro"\vn at any other place ; indeed, it is only after they 

 have been steeped a year or two in the muddy ponds (claires) of the 

 river Seudre that they attain their much-prized green hue. The ponds 

 (claires) for the manufacture of these green oysters — the oyster par 

 excellence^ according to all epicurean authority — require to be watertight, 

 for they are not submerged by the sea, except during very high tides. 

 Each claire is about 100 ft. square; the walls for retaining the waters 

 require, therefore, to be very strong. They are composed of low banks 

 of earth, 5 or 6 feet thick at the base, and about 3 feet in height. 

 Tliese walls are also useful in forming a promenade, on which the 

 "watchers or workers can walk to and fro and view the different ponds. 

 The floodgates for the admission of the tide require also to be thoroughly 

 watertight and to fit with great precision, as the stock of oysters must 

 always be covered with water, but a too frequent flow of the tide over 

 the ponds is not desirable, hence the walls, which serve the double 

 purpose of both keeping in and keeping out the water. A trench or 

 ditch is cut in the inside of each pond, for the better collection of the 

 green slime left at each flow of the tide, and many tidal inundations 

 are necessary before the claire is fit for its stock. The oysters placed in 

 them are a year or sixteen months old, and it is two years at least before 

 they are properly greened. 



