430 THE POPULAR SCIENCE MONTHLY. 



While these devour the banquet death has spread for them, while 

 forests of confervoid threads rise in silken tufts like microscopic sa- 

 vannas, Nature is passing portions of the ichthyic debris through her 

 laboratory, and the very source of life for which they pined and 

 perished oxygen is poured in in large measure, and the corruption 

 is quickly changed to sweetness. Of the once sportive fishes some 

 portions have become air, other portions have become water, but the 

 chief of their bulk lives already in the vegetation which hides their 

 grave, and the moving throng with which that vegetation is peopled. 

 God's purpose, in the working of the laws in obedience to which these 

 changes have taken place, is manifestly to keep ever true that balance 

 of life and death of which He holds the beam in His own hands. 



But my aquarium which has not thus been interfered with presents 

 already a similar scene of life and bustle. When first supplied, the 

 milky-looking water was abundantly full of gaseous matters, and every 

 part of the rough rockwork was, for a time studded with silvery 

 globules. The fishes consumed all that in the process of breathing. 

 As the water passed through their gills, the oxygen was absorbed ; 

 that oxygen, by a process of refined chemistry, and perhaps by the 

 help of iron also, gave their gills a bright-red color, gave their blood 

 its red color too, and, by other processes not less refined, sustained he 

 balance of life's functions within them, for without it they must perish. 

 We believe that not the airiest particle of earth, atmosphere, or water, 

 nor the most minute globule of condensed moisture, nor the most in- 

 finitesimal point of meteoric dust, can ever be lost, at least during 

 Time, from the fabric of the universe. My fishes tell me that the 

 oxygen they absorb from the water they again return to it, but in 

 another form. They Aspire oxygen and empire carbonic acid, just as 

 a man does, and every other living creature that moveth upon the 

 face of all the earth. Is it within the reach of human power, even 

 when reason, imagination, and fancy combine together as a bold triad 

 to look direct upon a fact, to appreciate that principle of terrestrial 

 life by which animal and vegetable organisms reciprocally labor to 

 maintain the balance of atmospheric purity ? The carbonic acid given 

 off by the animal is poison to it, if it accumulate while the supply of 

 oxygen is cut short. It was carbonic acid as much as absence of oxy- 

 gen that killed our fishes just now, for, though inhabitants of water, 

 they were not the less suffocated. Therefoi*e I see tohy, in the tank 

 that has been left alone, plants have cast anchor on the glass walls, 

 the brown pebbles, and the gray blocks of sandstone-rock. My fishes 

 breathe and breathe. If their numbers are properly proportioned to 

 the area they occupy, they will never exhaust the water of oxygen, 

 never render it fetid with carbonic acid, so long as one necessity of 

 vegetable life light is allowed to use its active influence to paint 

 the plants green, even as oxygen gives a sanguine hue to the gills or 

 lungs of the fishes. To those plants, the carbonic acid, which the fishes 



