DISTURBANCE OF NATURAL BALANCES. 143 



ons whenever lie interferes with arrangements pre-established 

 by a power higher than his own. The equation of animal and 

 vegetable life is too compKcated a problem for human intelligence 

 to solve, and we can never know how wide a circle of disturbance 

 we produce in the harmonies of nature when we throw the 

 smallest pebble into the ocean of organic being. 



This much, however, the facts I have hitherto presented au- 

 thorize us to conclude : as often as we destroy the balance by 

 deranging the original proportions between different orders of 

 spontaneous life, the law of seK-preservation requires us to re- 

 store the equilibrium, by either directly returning the weight ab- 

 stracted from one scale, or by removing a corresponding quantity 

 from the other. In other words, destruction must be either re- 

 paired by reproduction or compensated by new destruction in an 

 opposite quarter. 



The parlor aquarium has taught even those to whom it is but 

 an amusing toy, that the balance of animal and vegetable life 

 must be preserved, and that the excess of either is fatal to the 

 other, in the artificial tank as weU as in natural waters. A few 

 years ago, the water of the Cochituate aqueduct at Boston be- 

 came so offensive in smeU and taste as to be quite unfit for use. 

 Scientific investigation found the cause in the too scrupulous care 

 with which aquatic vegetation had been excluded from the reser- 

 voir, and the consequent death and decay of the animalculse, 

 which could not be shut out, nor live in the water without the 

 vegetable element.* 



* It is remarkable that Palissy, to whose great merits as an acute observer I 

 am happy to have frequent occasion to bear testimony, had noticed that vege- 

 tation was necessary to maintain the purity of water in artificial reservoirs, 

 though he mistook the rationale of its influence, which he ascribed to the 

 elemental " salt " supposed by him to play an important part in all the oper- 

 ations of natiire. In his treatise upon Waters and Fountains, p. 174 of the 

 reprint of 1844, he says: "And in special, thou shalt note one point, the 

 which is understood of few : that is to say, that the leaves of the trees which 

 fall upon the parterre, and the herbs growing beneath, and singularly the 

 fruits, if any there be upon the trees, being decayed, the waters of the par- 

 terre shall draw unto them the salt of the said fruits, leaves, and herbs, the 

 which shall greatly better the water of thy fountains, and hinder the putre- 

 faction thereof." 



