PREPARING THE TANK. ol 



of the vessel, but merely to sink it well in the sand and 

 gravel, so that it may be held upright, as an Aquarium is 

 not generally intended to be moved ; and if rockwork be 

 well set up there will be no danger of its falling, unless the 

 tank gets a shock that would be dangerous to the joints 

 A very good plan to make up rockwork in a marine Aqua- 

 rium is, to set up two stones for a cromlech (as I have 

 described) and use, for the upper flat one, a large stone 

 upon which one or more kinds of sea-weed are growing 

 and an end of which maybe made to project a little above 

 the surface of the water, for the purpose of allowing crab; 

 and other animals that prefer it to come out into the air 

 when they wish. I have found such stones as I speak of 

 which have had growing upon them plants of Viva, Entc 

 romorpha, Ptilota, Cladophora, and one or two others ; such 

 stones can be procured on any rocky coast where the Alga 

 are plentiful : for instance, on the shores of New York 

 island, as, indeed, I shall more particularly mention in the 

 chapter on collecting specimens. 



Aspect. — Having now prepared the bottom and set up the 

 rockwork of our miniature pcud or ocean, we must find 

 out if we have it placed in the best position, suitable to 

 its well being, as it is never advantageous to move the 

 tank when it is once arranged and filled, as doing so may 

 stir up the sediment that collects at the bottom, and, be- 

 sides, frighten the fish. If we have a window facing the 

 east, and from which the sky can be seen without dislo- 

 cating our necks, we should place our Aquarium there, a* 

 both animals and plants like to get the rays of the morning 

 sun, and always thrive the better for them. We masi 

 guard, however, against the heating power of the rays : 



