4854 THE ZooLoGist—APRIL, 1876. 
all see the water introduced by the two methods: jirst, by that 
simple and well-understood law of gravitation by which water 
always seeks and finds its level: by this simple power it flows 
from tank to tank until it reaches the lowest, when it plunges into 
the dark reservoir underground, thence to be pumped up again 
into the highest by steam power, to recommence its descent. This 
is essentially the “ circulating system,” the water being constantly 
in motion,—in fact, being a sea-water stream, always running in a 
ring,—and, were it not for the apparent contradiction in terms, 
I should say always fresh and health-imparting. 
The second method is also achieved by the power of steam, which 
drives a second and a smaller stream of water into each tank with 
such force that it carries atmospheric air with it to the depth of two 
feet, more or less, below the surface of the water already in the 
tank ; by this process the air becomes divided into minute bubbles 
—infinitesimally minute they certainly are. These bubbles, after 
descending as low as the force exerted can possibly impel them, 
quietly reverse the direction of their course, and ascend in the 
most deliberate manner to the surface, thus presenting a spectacle 
exactly similar to that produced by throwing silver sand into water, 
but the air moving in an opposite direction to the sand—upwards 
instead of downwards—a beautiful and interesting spectacle is pre- 
sented—one which often takes the spectator by surprise as being 
contrary to the laws of gravity for the supposed sand to rise 
towards the surface of water. Were not this second process super- 
added to the circulating process, the two systems might be fairly 
contrasted, but when either of the aquariums possesses the merits 
and advantages of both, surely all comparison and contrast is out 
of the question: when you desire to test the respective merits of 
two horses you do not harness them abreast: the Crystal Palace 
does this because it does not aim at competition, and therefore 
superiority is inevitable. Were not this process superadded to the 
circulating process the two systems of management might be fairly 
contrasted ; but as the matter stands the Crystal Palace has all the 
advantages of the circulating system combined with the most per- 
fect aération that has yet been devised: it would therefore be more 
exact to say that Brighton makes use of but one system while the 
Crystal Palace avails itself of both. 
Having set this matter in its proper light, I proceed to quote, 
in evtlenso, Mr. Kent’s remarks on the culture of whitebait, 
