32 rilEPARING THB TANK. 



keep it in place ; and for this purpose I have found the 

 white quartz pebbles, that arc picked up on the sea-shore, 

 the best— but even they, as well as the sand, must be well 

 washed, to remove all salts or decaying animal or vege- 

 table matter. The sand is useful in the case of the fresh 

 water Aquarium to set the plants in, and the pebbles to 

 keep them in place and steady. 



Though it may at first sight appear to be so, it is not 

 a matter of small importance as to the amount and quality 

 of the soil or bottom employed for Aquaria; and though 

 many of the fresh-water plants have no apparent roots, 

 and others seem to flourish just as well when they are torn 

 away from the roots and thrown into the water to take 

 their chance, yet it is certain that some plants have pecu- 

 liarities that fit them for growing in a soil of a particular 

 kind, and, consequently, they will not flourish, though they 

 may, to all outward appearances, grow in a soil of a dif- 

 ferent description : thus, the glass-wrack (Zostcra marina) 

 although it seems to grow in the sand beneath the mud, 

 will not flourish in aa Aquarium unless there be that mud ; 

 and, in the fresh-water collection, there is the water plan- 

 tain (AUsma plant a go), the water violet (Hottonia palus/ris), 

 the water lilies, both white and yellow (Nympktm alba and 

 Nwphar lutcum), aud the common arrow-head (SagiMa/ria 

 sagittifolia), besides many others that will not flourish in 

 any but a deep soil at the bottom of the tank. Therefore, 

 the soil must be regulated according to the plants which 

 are intended to be grown in the Aquarium. The kind of 

 soil or bottom that I have described above will be found 

 to be the best to be placed in a tank for ordinary pur- 



