614 Aquaria: Their Past, Present, and Future. [ October, 
mental glasses, for then they would have been constantly kept at 
an even temperature and in a state of constant aeration. This 
would have done away with the necessity of the everlasting wip- 
ing and washing of the glasses; and, they being thus left alone, 
and in a certain amount of daylight, vegetation would soon have 
appeared in them, stimulated by the action of that light, without 
having, been visibly introduced, but present everywhere in the 
seeds or spores of plants, merely waiting to be developed. Such 
an arrangement, indeed, would have been precisely that of the 
best modern aquaria as now-made, in which the water is so con- 
tinually and abundantly aerated by ceaselessly moving machinery 
that impurities have no.time to accumulate, but are oxygenated 
and dissipated as quickly as they form. In the Brighton and 
Havre public aquaria, the old and intermittent system used by 
Dalyell has been reverted to, and of course with ill results, as 
the water freshly obtained from the sea is turbid when seen in 
large masses, and is unhealthy for the animals, only a small 
number of which therefore can be kept in great bulks of fluid, 
because it is insufficiently aerated. This will be the case also 
at the Scarborough aquarium, now being built on the same erro- 
neous principle. 
Dalyell, however, was no mechanician or physicist, and he 
knew nothing of marine botany; so he just did as his neighbors 
did with their fresh-water gold-fish globes; he changed the 
sea-water and threw it away as quickly as it became sullied, and 
this water he obtained at no great cost, he living close to the sea- 
Or if the cost of time in getting it was considerable in proportion 
to the work done, i. e., the quantity obtained, it mattered not 
much to him, as he was a rich man. Yet, had he but known 1t, 
the sea-water he thus obtained was less good for the animals he 
kept than it should have been, inasmuch as it was from the 
adjoining Firth of Forth, and of the density of but 1.024, at a 
temperature of 60° F.; whereas had he kept it for some months, 
it would have evaporated to the more proper density of 1.027 at 
60° F., taking distilled water as being 1.000 at 60° F. : 
I have given this narration as showing the state of things 
aquarially at the end of the last century, and during the first 
half of the present one, and also as being the mode of operation 
which the general public, and even the great mass of the higher 
and better educated classes of society, still believe to be the sy8- 
tem necessary to be followed in the maintenance of aquaria. 
In the year 1842, the late Dr. N. B. Ward published the first 
