24 T. C. WHITE ON THE AQUARIUM 



importance, yet will be of great service — a specific gravity bubble, 

 that will just sink in sea water of tbe rigbt density, may be kept 

 in your tank ; if it floats to tbe top of tbe water you may know 

 tbat tbe water bas evaporated and become too salt, when it will 

 require diluting with fresh water till the bubble slowly sinks again. 

 Many mark the side of the tank by gumming a piece of paper at 

 the level of the water, but this method is not sufficiently delicate. 

 I have recently added a means of injecting atmospheric air into 

 my Aquarium, which serves the double purpose of aerating the 

 water and creating a current in it, which seems to be appreciated 

 by my anemones, and it may be of service to describe it. At one 

 end of my Aquarium, and just above high water mark, a hole has 

 been drilled through the slate and a piece of tin gas pipe cemented 

 in ; it is left projecting about one inch on the outside, and on the 

 inside just sufficient to carry a length of glass tubing about the 

 diameter of an ordinary quill ; this is bent at several angles to 

 enable it to lie safely along the sides and bottom of the tank, and 

 at its extremity is bent, so that its end, drawn in a gas flame to a 

 capillary point, projects into the middle of the water. To the 

 metal tube on the outside of the Aquarium a piece of elastic tube, 

 attached to an india-rubber bellows, is fixed, and by this means I 

 am. enabled to drive a stream of air into the water till it appears 

 effervescing ; the fine bubbles from the spray remain in suspension 

 for hours, and become ultimately absorbed. This apparatus, 

 although not absolutely necessary, is attended by such good re- 

 sults that I recommend its adoption ; but a great deal of benefit 

 arises from syringing the water with a glass syringe. And now 

 for a few words on the third division of my subject — the Occupants 

 of tbe Tank. If you add nothing more to your Aquarium than 

 what will be found growing and multiplying, as it were spon- 

 taneously, you will have abundant material for microscopical obser- 

 vation. I have been enabled in mine to watch the conjugation and 

 multiplication of some of the Diatornaceze, the development of the 

 Foraminifera, the growth of the germs of the Marine Algaj, tbe 

 development of the Polyzoa, and the various transitional stages 

 through which all these forms of marine life pass; these, and 

 many other subjects of study, a successfully-established Aquarium 

 would afford, and if, after the example of Drs. Drysdale and Dal- 

 linger, these researches were recorded, and every change faithfully 

 drawn and preserved for future reference, abundant light would be 



