ANIMALCULAR LIFE. 145 
spontaneous life, the law of self-preservation requires us to re- 
store the equilibrium, by either directly returning the weight 
abstracted from one scale, or removing a corresponding quan- 
tity from the other. In other words, destruction must be either 
repaired 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 well as in natural waters. A few 
years ago, the water of the Cochituate aqueduct at Boston be- 
came so offensive in smell 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 
reservoir, and the consequent death and decay of the animal- 
cule, which could not be shut out, nor live in the water with- 
out the vegetable element.* 
Animalcular Life. 
Nature has no unit of magnitude by which she measures her 
works. Man takes his standards of dimension from himself. 
The hair’s breadth was his minimum until the microscope told 
him that there are animated creatures to which one of the hairs 
of his head is a larger cylinder than is the trunk of the giant Cali- 
* It isremarkable that Palissy, to whose great merits as an acute observer 
I am happy to have frequent occasion to bear testimony, had noticed that 
vegetation was necessary to maintain the purity of water in artificial reser- 
voirs, 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 ope- 
rations of nature. 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 putrefac- 
tion thereof.” 
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