SECRETARY'S REPORT. 209 



and its agricultural value depends on many causes. These may 

 be resolved into four classes, depending on — 



1st, Organic matter, chiefly animal. 



2d, Soluble salts. 



3d, Silicates. 



4th, Shells, or carbonate of lime. 



First, the organic matter, independent of that of the living or- 

 ganisms inhabiting the shells, is a very small amount, probably 

 from two to three per cent. This becomes ammonia, and gives a 

 definite value to the mud which analj'sis only can determine. 



Second, soluble salts of potash, soda, lime, magnesia, exist in 

 'inud as chlorides and sulphates, but probably in no case exceeding 

 one per cent, for any element, yet all valuable as affording essen- 

 tial constituents of plants. 



Third, silicates. We may dismiss this class with the remark 

 that they are identical with those of all soil ; they contain phos- 

 phoric acid. Analyses of such marine deposits, after removing the 

 organic matter and soluble salts, have shown that they contain all 

 the inorganic elements of plants. If any effect of muscle bed is to 

 be attributed to the silicates, it is due to their physical state. I 

 should attribute much to this if the quantity used was enough to 

 act mechanically. Probably one-half to three-fourths of this class 

 will be found to consist of sand and clay, and a portion of its silica 

 is in a soluble state. 



Fourth, shells or carbonate of lime, either whole or comminuted, 

 dead or alive, forms a large portion of muscle bed. Analysis will 

 show, I venture to predict, at least twenty per cent. If, now, 

 we attempt to explain the known effects of muscle bed by refer- 

 ence to the action of either organic matter, salts, or silicates, or to 

 all these, it should be equall}'- serviceable to all lands destitute of 

 these elements. This would be to refer its action simply to its 

 viud. Such mud, even dock mud, according to Mr. Bailey, (see 

 your report, 1859,) does good to sands and clays. As I under- 

 stand it, muscle bed shows its effects chiefly and signally on clay 

 land, or loams underlaid by clay. How is this to be explained ? 

 Easily by reference to this fourth class. 



(a) What is clay? Alkali, alumina, silica — a compound silicate 

 of these elements, its alkali being chief!}' potash. 



It is well established that carbonate of lime decomposes clay, 

 and frees its alkali. A dressing of muscle bed is like an annual 

 sprinkling of wood ashes. This effect will continue as long as the 

 shells last. The experience of Mr. Wasson shows this to be about 

 twenty years. 



(&) Carbonate of lime decomposes the common salt and other 

 chlorides of the mud. It lets loose its soda and magnesia. It will 

 have this effect not only on the salts already in the bed, but upon 

 like salts always brought in by the ocean spray, dew, and rain. 

 The original stock of these is thus more than kept up. Who sows 

 muscle bed, sows carbonate of soda. 



(c) Carbonate of lime, porous soil, and animal matter are the con- 

 ditions of nitre making. So long as muscles decay we have the 



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