1876.] Aquaria: Their Past, Present, and Future. 613 
residual oxygen being liberated for the use and benefit of the 
animals. Thus the ocean, and rivers, and lakes, and all other 
waters in nature, of varying degrees of freshness and saltness, 
by motion and vegetation, both originating from the sun, are 
maintained sufficiently pure and respirable. l 
These operations were going on almost at Dalyell’s door, yet 
he did not learn to apply them to practice, as he migh} have 
done. What he did was this: He fed the animals in his jars on 
mussel flesh, which is easily diffusible in water, and which 
quickly makes it milky; and this, with the absence of growing 
Vegetation, and the breathing and other emanations of the 
animals, soon caused the water to become offensive in appear- 
ance and in smell. So he threw it away. But the very act of 
pouring it, and the motion of it as it trickled onward to the sea, 
purified it, because such an act was an unconscious imitation 
of what nature does. Had Sir John but thought of the merely 
Vehicle character of water, and of its incapability of being de- 
composed save by a very slow and expensive process, he would 
at once have seen that the minutely disseminated mussel flesh 
and its juices in the water made that water unfit to support life, 
only temporarily. : It was not the water itself that was not fit ; 
it was only something in the water that was wrong, and if that 
Something were removed the water would be left as good as ever. 
If, therefore, instead of sending it back into the sea by a long 
toad, and then going to the immense pains to dip it back again, 
he had poured it into a large receptacle in his own house, such 
Teceptacle or reservoir being many times larger than the aggre- 
gate contents of all his glass jars, he would have found that in a 
short time he would have possessed a source of supply for the 
Jats quite as good as the ocean provided. Had he, in addition, 
Placed his reservoir in a cool cellar, and had a pipe connecting it 
with the study to which Miss Dalyell has incidentally alluded, 
with a funnel at the upper end of the pipe, in which was placed 
à piece of straining-cloth or a small hair-sieve, to arrest the 
“arser pieces of decaying organisms, and if he had poured the 
| Water he had usedʻinto this funnel, the arrangement would have 
been still better. Yet better would it have been had he pos- 
%ssed another pipe. leading upward from the reservoir, through 
Which he could pump up the sea-water as he wanted it. Best of 
* Would have been some form of incessantly-working machinery, 
by means of which the water would be always coming up, day 
F 8 night, from this large and cool reservoir into the experi- 
