176 CALCAREOUS MANURES— APPENDIX. 



account for these waters being more deeply colored than those which pass 

 by a more rapid descent to James river. But these different circumstances 

 do not serve at all to explain why the latter waters should soon lose, if they 

 had it at first, the slightest trace of color. 



The like circumstances are probably to be found to more or less extent 

 in most of the counties on our tide-water rivers, as most of them have poor 

 forest lands and some swampy streams in the interior. 



As the opposite circumstances of the presence or absence of color in 

 different waters is certainly not caused by such difference in the sources of 

 supply, they must be caused by some subsequent action which serves to 

 clear the waters in one locality, by combining with and taking off the dis- 

 solved coloring matter, and which action does not take place elsewhere, 

 because there is no such etffcient agent present. That agent I take to be 

 carbonate of lime, or some other salt of lime in the soil in the one case, 

 and which is present in quantity altogether insufficient for such action in 

 the other case. According to the views which were presented (page 58) 

 in regard to the power of calcareous earth to combine chemically with 

 vegetable matter, if the colored waters should flow over soils furnished with 

 calcareous matter, or into streams impregnated with any salts of lime, it 

 would follow that the suspended or dissolved vegetable extract would com- 

 bine with the calcareous matter of the soil in the water, and the new com- 

 bination be precipitated, and be given to the soil, as manure, either imme- 

 diately or remotely. This effect would be greatly aided if the streams 

 swollen by rains actually passed in contact with and washed away exposed 

 banks of marl. All recent rain water contains a small amount of carbonic 

 acid, and that impregnation enables water to dissolve a proportional quan- 

 tity of carbonate of lime, which is insoluble in water without this addition 

 of carbonic acid. Therefore, in such circumstances the swollen streams 

 and land floods v/ould necessarily dissolve some carbonate of lime, which 

 would be thus placed immediately and fully in mixture and perfect contact 

 with the before dissolved vegetable coloring matter, and next must take 

 place the combination of the two, and precipitation of the compound ma- 

 nure. The consequence must be, that the lands thus overflowed must be 

 more or less enriched by every heavy rain ; while the lands overflowed by 

 the colored waters receive, or retain, nothing of soluble vegetable matter from 

 this source, and may even lose part of what they had before received from 

 the decay of their own growth, or other sources, by its being dissolved 

 and carried off' by such overflowing waters. 



Now let us see how the actual results agree with these different causes, 

 so far as the causes are known to exist. In the limited region particularly 

 referred to above, the low grounds, subject to inundation by rains in a 

 state of nature, and having beds of marl which the stream cuts through, 

 are of much richer soil than any others, though the quantity of marl displaced 

 by the stream (if indeed any such displacing be perceptible) would seem 

 altogether too small in amount to produce such extent of fertilization by 

 direct action. And it is believed, whether marl beds be so exposed or not, 

 that the low-grounds on the streams of colorless water are always much 

 better soils, and of more durable fertility, than those washed by colored 

 waters. The latter soils being often swampy, are full of vegetable matter, 

 and of course would be very productive when first drained and cultivated. 

 But these soils are far from being among the most durable, and they are 

 even at first, and when in best condition, very inferior lands to most low- 

 grounds of prime quality ; and the latter are always penetrated by streams, 

 or had been sometimes covered by floods, which, however turbid at certain 



