132 Preparation of Sea Water for the Aquarium. 



added to the contents of the aquarium. There would be no 

 difficulty in supplying bromides and iodides, as the bromide 

 and iodide of potassium may be procured from any druggist. 



It is of course quite possible that in a single aquarium the 

 death of a certain portion of the animals might furnish cal- 

 careous salts or silica for the skeletons of their survivors,* 

 and in like manner, the death of a given number of the 

 plants might liberate iodides and bromides for the remainder ; 

 but the object of those who maintain aquaria, I presume to 

 be, the rendering as certain as possible the vigorous develop- 

 ment of all its living contents, and this could only be secured 

 by some such arrangement as I have proposed. 



As aquaria are now attracting much attention among natu- 

 ralists, I would suggest the desirableness of some of them 

 trying how long animals will live in sea water made strictly 

 after Mr Gosse's recipe, and without any calcareous or sili- 

 cious fragments at the bottom of the vivaria. Those observ- 

 ers also who record their success with artificial sea water 

 should be as careful in stating the chemical composition of the 

 stony fragments laid at the bottom, as of the water employed 

 in filling their aquaria. In their aquarian experiments hither- 

 to, naturalists have guided themselves chiefly by the results 

 of the chemist's analyses of sea-water. But these supply 

 but one-half of the requisite data : the naturalist should have 

 equally regarded the analyses of marine plants and animals ; 

 for if any substance is invariably found in them, it must as 

 invariably be furnished in the liquid or solid contents of 

 the aquarium. The minuteness of quantity in which par- 

 ticular ingredients occur in living organisms can only be a 

 reason for furnishing them in minute quantity not for omitting 

 them altogether. 



* Mr Gosse observes that carbonate of lime " might be found in sufficient 

 abundance in the fragments of shell, coral, and calcareous alga? thrown in to 

 make the bottom of the aquarium" but he nevertheless refers to it as one of 

 those substances which he thought he "might neglect from the minuteness of 

 their quantities." The practice here corrects the error of the precept, for the 

 calcareous fragments would furnish not only carbonate of lime, but salts of 

 magnesia, as well as phosphate of lime and fluoride of calcium. 



