This aquarium was in appearance somewhat like an inverted dish-cover of glass--one of the best shapes to be had. This sort being free from those leaky joints that are the invariable accompaniment of all-square cisterns; while globular ones have not got sufficient space at the bottom for rock-work, or those little hiding-places that delight the hearts of the denizens of the deep when they are free agents and in their own waters. Presently, under the active superintendence of the old sailor, the whilom empty glass receptacle began to assume a more picturesque aspect. To commence with, a groundwork was constructed of fine white sand and shells, each of the latter being washed in repeated baths of clear and fresh sea-water, which had been brought up from the beach in the morning, before being introduced into the aquarium; where, if success be desired, cleanliness is as essential to the well-being of its little tenants as it is deemed to be amongst human beings. The Captain said something to this effect while making Nellie wash the different shells, which he then arranged along the sandy bottom, which was made to slope from the back of the structure down to the centre, forming a sort of hollow there; and then rising again in front. "So far, so good," said the Captain, placing some bits of rock in the background, which, leaning against each other, formed so many small caverns. "These will do for those crabs, which Master Bob insists on having, to retreat to when some of the other fry pay them too much attention." On the right and left of the aquarium the old sailor dexterously built up larger pieces of rock-work, intermixed with bits of red seaweed that grows in the form of a feathery plume, called by naturalists the "bryopsis plumosa," than which no more graceful marine plant can be found. Close to this and serving as a contrast, the Captain placed the green laver he had made Nell pick up at the last moment when they were leaving Seaview and running to catch the steamer. "This chap, styled the `ulva latissima' by the scientific gentlemen who manufacture such titles, is a capital thermometer," said the Captain on putting in the laver. "You'll find he'll always rise to the surface when the weather is bright and sunny; while he sinks back to the bottom, as I've put him now, on its being damp and overcast." In the more immediate foreground, a number of little starfish squatted about on the miniature strand that shelved down from the rocks, arranged with much care to the general spectacular effect by Nellie, who was most painstaking in the matter.