MARL. 



113 



There are in this country some substances used 

 largely as manure, and called marls, that have very 

 little lime in them. These are in certain parts of 

 New Jersey. The lime, in shells scattered through 

 them, varies from 10 to 20 per cent in some speci 

 mens, in others there is scarcely any at all. The effect 

 of these marls is, however, great upon poor soils, and 

 in New Jersey they are very largely applied. The 

 secret of their value lies chiefly in from 12 to 20 per 

 cent of potash, which the best of them contain, ac 

 cording to the analyses of Prof. H. D. Rodgers. 



It is always easy to ascertain whether any substance 

 supposed to be a marl, really is so or not, bytrying it 

 with a little muriatic acid. If there is much carbonate 

 of lime, the effervescence will be strong and violent, 

 owing to the bubbling up and escape of carbonic acid 

 gas. Carbonate of magnesia and many other car 

 bonates would, it is true, produce a like appearance; 

 but these are rarely found native, in very large quan 

 tities. 



On some sections of the sea-coast, a species of shell 

 or coral sand is to be obtained, made up of shells or 

 corals ground into fine fragments by the action of the 

 sea: this is always a valuable manure. On the coast 

 of Ireland, the fishermen go out and scoop it up from 

 a considerable depth. It contains usually some organic 

 remains, which add materially to its value. This, like 

 the marls, may be safely added to the land in large 

 quantities, without fear of injury to crops. 



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