28 



THE FAMILY AQUARIUM. 



some piscatory prison-baste/^ The cover will also keep 

 the dust from temporarily disfiguring the surface of the 

 water. It might be dispensed with, perhaps, without 

 much impropriety, as the dirt soon settles down to the 

 bottom of the tank ; but we prefer its presence, whether 

 made of fine muslin or of glass. It adds a neatness and 

 finish to the Aquarium ; and if simply laid over the top 

 of the vessel so as to permit the gases to escape, and oc- 

 casionally removed so as to allow a change of the superin- 

 cumbent air, it will be found both useful and ornamental. 



Double tanks, it has been suggested, might be so con- 

 structed that the water would, to a certain extent, imitate 

 the ebb and flow of the tide, by running regularly first 

 into one division and then into the other. This alterna- 

 tion of high and low water might serve to develop some 

 very interesting phenomena connected with those plants 

 and animals whose natural habits are associated with such 

 a change. There are marine animals whose organization 

 demands an entire or partial exposure to the air, and this 

 mode of gratifying their instincts might prove more effec- 

 tive than the usual one of supplying them with rockwork 

 sufficiently elevated to enable them to reach and enjoy our 

 rarer atmosphere. There are plants, too, which will not 

 thrive in tranquil waters. Sir John Paxton, knighted for 

 his successful conception of the plan of erecting the novel 

 building so renowned and imitated as the Crystal Palace, 

 discovered this fact when he was a simple florist to the 

 Duke of Devonshire. A gigantic S. American water-lily, 



