THE MARINE AQUARIUM. 149 



the pressure of the atmosphere, out at the fine orifice 

 and forms a jet iVeau, which can be directed to any 

 part of the tank. From passing thus in several fine 

 streams through the air, the water gets well aerated ; 

 and if the bell-glass be sufficiently large, our miniature 

 fountain will continue to play for. an hour or more. 



It will be found useful to have as adjuncts to our 

 Aquarium a net about three inches in diameter, made 

 bv stretching a bag of fine bobbinet over a wire ring 

 and attaching it to a wooden handle ; a pair of long 

 wooden forceps will also be found useful, both of these 

 servin"- to remove dead fish and portions of sea-weeds 

 that would otherwise decay and overturn the economy 

 of our collection. 



Filtering. — When sea water is used, and, indeed, some- 

 times it will be so with the artificial article, it will 

 prove muddy or not clear from some minute floating bodies 

 that it would take days to deposit. If we do not wish 

 to wait so long, we can resort to filtering in order to 

 render the water clear ; and this is done by suspending 

 over the tank a perfectly clean clay garden flower-pot, 

 which has a portion of sponge thrust into the hole, and, 

 over the bottom, a layer of powdered wood-charcoal. 

 If the water is allowed to pass through the charcoal 

 and sponge, it will be found to be perfectly clear and 

 well aerated at the same time. As Mr. Ilibberd remarks, 

 "With the river tank, the simplest way of reviving 

 exhausted stock is wholly or partially to change the 

 water ; with the marine stock, such a change . is not easy, 

 and the filter comes more legitimately into use, as already 



