OF WATER FOR ORGANIC MATTER. 81 



stances. It has already been shown that the carbon and 

 the nitrogen may entirely disappear, the phosphorus may 

 be precipitated,, and the sulphur be, to a large extent, re- 

 moved, nothing whatever remaining of the original sub- 

 stances except alkalies, some of the alkaline earths, and 

 chloride of sodium, or common salt. The latter in reality 

 is the only substance which, so far as I know, is neither 

 dissipated nor precipitated in whole or in part, potash ex- 

 cepted. The common salt, therefore, may be taken as 

 an indication of the amount of original or organic matter, 

 if we subtract from it any portion which we know to have 

 appeared originally connected only with inorganic sub- 

 stances. 



Perhaps all natural waters contain common salt, although 

 rain in a quiet day, and in a clear district, is nearly free 

 from it, perhaps in some places entirely so. In passing 

 through the soil it always collects some chlorides ; some 

 of these are the measure of the amount of vegetable 

 matter decomposing in the soil. If we were to estimate 

 the amount of chlorides dissolved by the salt alone out of 

 the inorganic soil, and subtract that from the total, we 

 should obtain the amount dissolved by the action of vege- 

 tation breaking down the rocks or soil. If the organic 

 matter were decomposed, the common salt would still flow 

 down the streams and tell its tale. These quantities, 

 however, vary excessively on every soil and in every 

 climate, and with every wind and degree of wind. 



The common salt which comes down our streams comes 

 from the wear and tear both of animals and vegetables in 

 the process of living. We cannot tell which came from 

 the animals and which from the vegetables. 



From pasture-land and land generally, the greatest 

 amount is from vegetation ; and if we collected the organic 

 matter, we should find also there that vegetation gave the 

 fi-reatest amount of matter, except from recentlv manured 



SER. III. VOL. IV. G 



