304 CALCAREOUS MANURES-APPENDIX. 



deposite of the rivers, and thereby increased the marshes both in breadth 

 and in height. More mills continued to be built, and on streams worse 

 and worse for water power, as the choice became less open, and the mill- 

 mania began to grow ; and, in the general, each successive construction of 

 a pond was less productive of profit, and more productive of disease, than 

 its predecessors. The number of mills not only continued to increase, and 

 is increasing to this day, and in the oldest settled parts of this state, as well 

 as the newest, but gradual changes also took place in the condition of the 

 old mills which greatly increased their fitness to produce disease. By the 

 long continued deposite of mud from the streams, and the washing of the 

 now cleared and tilled hill-sides, the ponds became more shallow, and the 

 waste of water by evaporation therefore became greater ; v/hile the supply 

 was lessened, in consequence of the extended clearings of the great forest 

 which had before covered the whole country. To remedy the increasing 

 deficiency of water, the owners of old mills, who were not prohibited by 

 circumstances, raised the level of their ponds; which, by increasing their 

 surface and their contents, still more increased the daily evaporation, and 

 also the violence of floods, and the variable height and surface of the water ; 

 all of which again combined to increase, still more than before, the product 

 of malaria. The consideration of the progress of all these circumstances, 

 and their bearing on each other, will serve to explain why a particular 

 neighborhood might formerly have been healthy, though having two or 

 three mill-ponds within or around it; and why it might gradually have be- 

 come very unhealthy, in the course of time, by the malaria produced by 

 the ponds of the same mills, or perhaps by the addition of one more pond 

 only to the former number. But, in such cases, so gradual would be the 

 general change, and so irregular and variaWe the attacks and virulence of 

 the autumnal diseases, that the sutTerers would not attribute the change, 

 (even if they admitted it to have taken place,) in their average degree of 

 health, to causes which had so long existed without being charged with 

 doing mischief; and in which causes no change of condition had been 

 observed. Add to this, that self-love makes every man reluctant to believe, 

 and to confess, that his own farm, or his own neighborhood, has become 

 more sickly ; and the change for the worse is attributed to transient causes, 

 until the former state of things is almost forgotten, and the present is re- 

 ceived as if it had always been the usual condition of circumstances. 



During all this time, other causes were working to produce other nurse- 

 ries of disease, and impediments to agricultural products and improvement. 

 The wet alluvial bottom-lands, bordering on small rivers and still smaller 

 streams, were for a long time neglected, and deemed of little value, except 

 for their fine white-oak, cypress, and other noble timber trees. These were 

 cut down so as to fall into or across the streams, when in reach, more often 

 than otherwise ; and in consequence of such obstructions, continually in- 

 creased in number for more than a century, the before open streams were 

 choked, and the bordering low-grounds converted to swamps; and those 

 which had been swampy at first were made still more so, by obstructing 

 the sluggish streams, and spreading them over the whole surface, and 

 causing that surface continually to rise by fallen trees and alluvium. But 

 wet as are such swamps for the greater part of the year, most of the surface 

 is dry in autumn ; and the scanty water is then stagnant in numerous pools, 

 until added to by the first heavy rain, or a flood from a mill-pond discharged 

 above. Of course all these circumstances added enormously to the pre- 

 vious annual decomposition of vegetable matter, and consequent production 

 of malaria. Such swamps as these, formed by nature and increased by 

 art, are those on the Chickahominy, Blackwater, and many other long but 



