[11] OYSTER CULTURE IN MORBIHAN. 953 
tive element, one of the most deadly enemies of the oyster; this element 
ismud. ‘“ Mud is a deadly poison to the oyster, whether large or small. 
* * #* What then is essential to the prosperity of the oyster? 
Very little, indeed; a solid object, and water, devoid of mud.”* We 
might multiply these citations from Coste, Fraiche, and others; upon 
this point all seem to be in accord. It may, therefore, appear paradox- 
ical when we state that, upon the coast of Morbihan, the oyster thrives 
only where. there is mud; the fact is incontestible; reproduction suc- 
ceeds only in the muddy estuaries, and good parks exist only in the 
sheltered places, almost covered over by slime. This assertion would 
appear improbable did it not admit of an explanation. 
With these preliminary remarks, we will proceed to a consideration of 
the conditions required of a shore in Morbiban, in order that it may 
answer for the general cultivation of the oyster. 
The sea bottom consists, for the most part, of mud, as is evidenced 
by the many soundings that have been made, and by the results of 
various explorations. It is also known that, in many of our rivers, as at 
Auray and in the Scorff and the Blavet, there are sloping shores, which, 
when the tide goes out, appear above the water as immense areas of a 
black or brown color, and into which one can easily sink up to his neck. 
Whence comes this fine flocculent mud, which has seemed, at times, to 
threaten the port of Saint-Nazaire, and whose action has been so diffi- 
cult to resist. Does it come from the rivers, or is it produced by the 
constant disintegration of the rocks and shores? Why does it invade 
the mouths of all our rivers and all our bays and creeks? Some good 
may arise from our pointing out general causes, at least, if not by the 
determination of all the questions, and this is all our subject demands. 
The constant wearing of the rocks, as in ages past, by the action of 
the sea upon the headlands, gives rise to three principal kinds of material : 
gravel, sand, and mud. These materials are carried along by the action 
of the waves. Gravel is moved only in times of heavy storms, when, 
lifted by the force of the waves, it is moved gradually along, until it 
finds a region of comparative shelter, where it remains buried. Sand 
is more frequently moved than gravel, but the strength of the waves is 
required to raise it and carry it along, and it needs a greater calm than 
the gravel, in order to fall to the bottom again. Mud, on the contrary, 
being fine and light, acts more as though it were in solution in the water, 
and remains suspended in it for a long time; carried along by the cur- 
rents, which have no power over sand and gravel, it penetrates into 
coves, estuaries, and rivers, where it is deposited in the eddies, con- 
stantly raising the level of the shores. With regard to the movement 
of the sea alluvium, we are able to make the following deductions: 
Whenever we desire to determine whether a bay or estuary is a region 
of actual calm, we have only to examine the character of the bottom. 
If the bottom is muddy, the region is a quiet one; if sandy, it must be 
* De la Blanchére, Culture des plage maritimes, 
