ARTIFICIAL AERATION. 283 



the various currents are diffused through the sea, and 

 even earned to considerable depths, before they rise 

 to the surface and become dissipated. Thus the 

 violent agitation of the sea is a powerful agent in its 

 purification. 



One of the simplest modes by which this object 

 can be effected, is the drip-glass. I have been accus- 

 tomed to suspend over the Aquarium, a perforated 

 bell-glass (I think it is called a bee-glass) of suitable 

 size, into the orifice of which a bit of sponge may be 

 pushed, or a cork drilled with small holes. The 

 cord which suspends the drip-glass passes over a 

 pulley at the top of the window, so as to be raised or 

 lowered at pleasure. Every morning sufficient water 

 from the Tank is drawn or dipped off, to fill the drip- 

 glass, which is then hoisted to its full height. The 

 contents run out in slender streams, or in a rapid 

 succession of drops, which, passing through some four 

 or five feet of air before they reach the Tank, become 

 effectually purified. 



A convenient mode of aeration is that effected by 

 strongly syringing the water. The instrument should 

 be at least 1^ inch in diameter, and should be raised 

 above the surface at every down-stroke. After a few 

 moments' work, the whole Tank will be quite white 

 with minute bubbles of air, resembling the sea when 

 the waves dash and boil among the rocks. 



The same purpose may be more efficiently accom- 

 plished at a slight expense, in a manner which would 

 greatly augment the elegance of the Aquarium. In 

 the engraving placed at the commencement of this 

 chapter, I have represented a Fountain- Aquarium, a 



