256 THE TANK. 



glass cliimney of an Argand lamp, and fastening a 

 well-fitted cork into one end for a bottom, on wliicli 

 I then poured black sealing-wax varnish until a 

 smooth water-tight surface was formed. These are 

 more convenient than wide-mouthed phials, as the 

 sides are more truly perpendicular, and we avoid the 

 unequal refraction produced by the thickened bottom 

 of a phial. 



For a conservatory, to which an Aquarium would 

 form an appropriate accessory, a vase-like form might 

 be given to a large tank. If the outline were octa- 

 gonal, the objects in the interior would be visible 

 through the plate-glass without the distortion caused 

 by unequal refraction, which is a great objection to 

 vessels with curvilinear sides. But in such a situa- 

 tion, the chief point of view would be from above the 

 surface of the water; hence the depth should be 

 comparatively small, and the sides might recede, so 

 as to increase the width upwards. 



A good many animals, especially Anemones, 

 Madrepores, Crabs and Annelides, may be kept in 

 broad and shallow pans, in which the water does not 

 exceed three or four inches in depth. The glass 

 pans used for milk are good for this purpose. I have 

 an earthenware pan with upright sides, about five 

 inches deep, in which I have imitated the broken 

 interior of a rock-pool, with irregular projections and 

 promontories of cement. One advantage of such a 

 vessel is that sea-weeds may almost be dispensed 

 with, the extensive smface of water absorbing a large 

 quantity of oxygen from the air. An oval foot-bath 

 of whiteware makes a capital Aquarium. 



