SS2 SHELL MARL. 



must he ascribed. It is well to lay this shell-marl upon the land 

 shortly after it is taken from the sea ; by long exposure to the air, 

 it suffers disaggregation and loses a portion of its good qualities. 



There is another kind of sea-sand called trez, which forms banks 

 in the neighborhood of Morlaix, and which is known under the name 

 of tanque on the northern shores of France, which is favorable to 

 vegetation, particularly after it has been washed and freed from the 

 greater part of tbe salt which it contains. It is thrown upon the land 

 in larger quantity than the marl. The small quantity of animal mat- 

 ter which It contains putrefies and is lost when it remains exposed 

 to the air for any lengtli of time, so that a distinction has been made 

 between fresh or live trez^ and old or dead Irez, the one being the 

 article as it comes from the sea, the other after it has been exposed 

 some time on the shore ; the article which has been exposed un- 

 doubtedly contains a smaller quantity of organic matter than that 

 which is quite fresh. This variety of sea-sand is particularly avail- 

 able upon close and clayey lands, which sometimes receive as many 

 as sixteen tons per acre with advantage ; lighter lands, of course, 

 require much less. 



Shells, sand, slime, and sea-weed, are not the only useful mate- 

 rials supplied to agriculture by the sea ; Jish, or their ojf'al, is fre- 

 quently employed as manure. The practice of manuring with fish 

 is very old, and is universal wherever it can be had recourse to. 

 I have already had occasion to say, that at the period of the con- 

 quest of America, the Spaniards found it established among the 

 Indians, on the shores of the Pacific ocean. The lands are oc- 

 casionally manured with fish along the sea-board of Great Britain 

 and Ireland, and the low lands of Lincohishire, Cambridgeshire, 

 and Norfolk, also receive occasional supplies of the same power- 

 ful manure. The offil of the herring fisliery, of cod, of skate, and 

 of the pilchard, in Cornwall, the dog-fish entire, and other kinds, 

 that are either less esteemed, or that are caught in quantities greater 

 than can be consumed as food, are all admirable manures. We have 

 been recommended to mix the fish or fish-offal with quick-lime ; but, 

 unless in certain circumstances, the practice is very questionable ; 

 the addition is probably only j)roper where the materials are ex- 

 ceedingly oily, as is the case with pilchards, herrings, <fec. : an 

 earthy soap is then formed which prevents the injurious effects upon 

 vegetation which wholly oleaginous matters scarcely fail to produce. 

 One analysis of codfish, which I made along with M. Payen, gave 

 us a proportion of azote of nearly seven percent. This, of itself, is 

 enough to explam wherefore the fiesb, the cartilages, and the bones 

 of fishes should be found such energetic manures. 



The slimc deposited by rivers also yields manure which may be 

 employed to much atlvantage. T'le jSile, which periodically inun- 

 dates the plains of Lower Egypt, «»wes its fertilizmg action to the 

 slime which it contains, and which it deposites before it again recedes 

 into its bed. On the banks of the Durance, the mud or slime depos- 

 ited by the river is carefully collected for distribution over the fields 

 iu it£ vicinity. I'h'^ waters of this river are frequently turbid and 



