270 MODE OF AERATING SMALL MARINE AQUARIA. 



A SIMPLE MODE OF AERATING SMALL MARINE 

 AQUARIA. 



Of the three modes of maintaining the water of an aquarium in 

 good order, viz. — by vegetation ; by circulation of the water ; or by 

 injecting air ; the first generally fails to maintain the balance if the 

 aquarium be at all crowded, whilst the second involves such expense as 

 to generally prevent its adoption. The difficulty which has hitherto 

 prevented the adoption of the injection of air has been the necessity of 

 some mechanism for maintaining it continuously. I have, however, devised 

 a plan which is simplicity itself, and can be constructed, for a few shillings, 

 out of glass and india-rubber tubes. The principle is that known as the 

 "Trompe." A stream of water falls in drops down a tube about Jin. in 

 diameter, and furnished with a funnel at the upper end. These drops of 

 water falling down the tube carry air with them. The bottom end of the 

 tube enters the top of a cylinder, from the top of which also issues the 

 compressed air, by a tube, and is conveyed by a tube to the aquarium. 

 From the bottom of the cylinder a tube conveys the water, and being 

 bent upwards, discharges the water at a certain height above the bottom 

 of the cylinder. "When the apparatus is in working order, the vertical 

 difference in height between the level of the water in the cylinder and 

 the discharging orifice, is exactly equal to the depth at which the air-tube 

 discharges the air into the aquarium. The aquarium being higher than 

 the cylinder, it is impossible that the water used, which may of course 

 be fresh water, should get into the aquarium. A oft. fall is sufficient to 

 drive the air to a depth of 6in. in the aquarium, and, as I have found from 

 experiment, six times the volume of water used, though this will, of 

 course, vary according to the depth to which it is injected. In my own 

 apparatus, one gallon of water will keep up a continuous stream of 

 bubbles, rising through the aquarium for from two to four hours, keeping 

 it perfectly clear and bright, and evidently delighting the animals. The 

 small quantity of water used renders it practicable even where the water- 

 works are not at command. It is only necessary to have two receptacles 

 for the water, one above and the other below, and when the water has 

 all run over into the lower one, to change them. In order to use a very 

 slow current of water, it is advisable to insert, just below the funnel, a 

 double syphon, which prevents air rising up the tube, and where 

 the water collects until its accumulated force is sufficient to drive the air 

 down the tube. This air injection may also be used to produce a 

 circulation of the water at the same time as aerating it. Thus, let two 

 vessels, A and B, be connected by a narrow tube below the water level, 

 and let the tube terminate in A, by an inverted funnel. Then, if the 

 discharge of. bubbles take place underneath this funnel, they will rise 

 through the tube and carry a certain quantity of water with them. A 

 piece of glass tube bent into a syphon will convey the water back again 

 into A. Any number of vessels can be interposed between B and A by 

 syphons, and the current; will be maintained through the whole. I shall 

 be pleased to show the apparatus at work to anyone interested in the 

 subject.— C. J. Watson, 34, Smallbrook Street, Birmingham. 



