368 BLACK WATERS. 



high level wood-land, and flowing off in temporary rivulets, is seen 

 to be coloured by vegetable matter even within a mile of James 

 river, just as it is found on the other lands sloping towards the 

 Blackwater. But in either and every known case of such dis- 

 coloration being caused, it is on poor and acid land. No such 

 effect takes place on calcareous or even neutral soil, no matter how 

 abundantly it is provided with dead leaves or other vegetable mat- 

 ter. Therefore it is jnanifest that it is not difference of locality, 

 but difference of soil, which causes the different effects of the 

 surplus 'rain-water becoming tinged, and remaining tinged with 

 vegetable extract, or otherwise remaining colourless. And also, 

 after the water has been so tinged, that it depends on the difference 

 of chemical composition in the soils over which it passes, or of the 

 streams into which it is discharged, whether the colour remains or 

 is quickly discharged. And, as already stated, this difference of 

 action and effect depends on the absence or presence of lime in the 

 soils or waters to which the coloured excess of rain-water flows. 



It is only in the surplus quantity of rain-water, or that which is 

 more than the soil can absorb, that this colouring matter is seen. 

 But it is not the less certain that all of the much greater quantity 

 of water from more gentle and more frequent rains which soak 

 into the earth, must also be more or less tinged with the colouring 

 matter of the leaves and other dead vegetable matter through 

 which the water passes, and must take up, in passing, all that is 

 then easily soluble, and not chemically combined with some other 

 body. Thus, every gentle and soaking rain probably carries into 

 the soil the greater part of all the then soluble vegetable matter, 

 and that only which is soluble is all that is then completely ready 

 to act as food for plants. The same rain, and the subsequent 

 chemical action of air and warmth, cause the decomposition of the 

 before insoluble vegetable matter to recommence, and in a few 

 days there is a renewed supply of soluble or extractive matter 

 formed in the vegetable cover of the soil, ready to be dissolved and 

 to be carried into the earth by the next succeeding rain. 



Such is nature's process of furnishing alimentary manure, or 

 the food of plants, to soils. And the source of supply is unlimit- 

 ed j for it is principally from the atmosphere and water, and by 

 fixing their elements (oxygen, nitrogen, hydrogen, and carbon), that 

 the vegetable growths of soils, and consequently all alimentary 

 manures, are formed. 



Enormous then as is the continual waste of vegetable ex- 

 tractive matter and manure that is caused by every heavy rain, and 

 wliich is always evident to the eye in the black waters of so many 

 ponds and streams, all this lost fertilizing matter rowst be in very 

 small proportion, compared to the greater quantity that is -carried 

 more gradually and frequently into the earth. Much the greater 



