SHELLS MUD. 281 



analogous to the last, and of which the value may be estimated from 

 the quantity of azote which they severally contain. This value once 

 determined, every farmer knows the quantity which he must lay 

 upon his land ; and lie thus proceeds upon a much more rational 

 foundation than when he takes for his guide one or other of those 

 vague and arbitrary indications that iiave been given. Sinclair, for 

 example, would have us lay on nine bushels of feather rubbish to the 

 acre, and Schwertz recommends from four to five times as much 

 more Nothing, in fact, is more arbitrary and uncertain than to 

 estimate sucii materials by the bulk ; it must be obvious that the 

 weight of a bushel of hide trimmings, of horn-shavings, and of 

 feather-rubbish, must differ very widely, not only with reference to 

 one another, but also according to the state of division in which each 

 is measured. As a general rule, it is by weight, and weight alone, 

 that the quantity of manure must be estimated. 



Shells and mud from the sea-shore and the bottoms of rivers, are 

 matters that are not often very highly azotized ; nevertheless they 

 may contain an equivalent of the all-important element, azote, which 

 may bring them near to wet farm-yard dung in point of value. The 

 abundance of such matters in certain situations makes them ex- 

 tremely useful. The alkaline and earthy salts, which they generally 

 contain in considerable quantity, also add to their fertilizing proper- 

 ties. The sea-sand which is employed in Brittany under the name 

 oi marl, (merl,) consists, in great part, of the remains of corallines, 

 madrepores, and shells, mixed with a few hundredths of highly 

 azotized organic manner. This marine marl is found in great 

 abundance at the mouths of the river of Morlaix, where there is a 

 considerable traffic carried on in the article. It is said to be repro- 

 duced, new banks of it being met with from time to time. It is 

 obtained by dredging from barges, and the process is only allowed 

 to go on from the 15th of May to the 15th of October, when the 

 quays of the town of Morlaix are seen covered with the produce. 

 It is carted to a distance of five leagues inland. A barge-load 

 weighing seven tons, sells at from 6^. Qd. to 8.y. This same species 

 of marl is now obtained upon the coast of Plancourtrez and in 

 the roads of Brest. It has also been discovered near the mouth 

 of the river Quimpert. It appears, finally, that the shell sand so 

 much employed by the farmers of Devonshire and Cornwall is of 

 the same essential nature. 



In the neighborhood of Morlaix, from five to six tons per acre of 

 this calcareous sand are employed upon light dry soils ; from eleven 

 to twelve tons are given to clayey lands. This quantity would 

 probably be too great for porous and damp soils, inasmuch as sea- 

 marl belongs to the class oi' warm manures ; that is to say, it under 

 goes speedy decomposition. There can be no doubt that sea-marl 

 acts further, in virtue of the calcareous matter which it contains, 

 and also of its merely mechanical properties upon the strong argilla- 

 ceous lands of Brittany, for which sand alone is an excellent im- 

 prover. It is also to the carbonate of lime which it contains, that 

 "Is good effects upon lands that show an inflorescence of iron pyrites 



24* 



