DESCRIPTION OF TBE LABORATORY AT PLYMOUTH. 99 



Fittings. 



The Tanli-room. — The tank-room is fitted with tanks of 

 slate and of glass fitted in cast-iron frames, and water is 

 supplied to these tanks through vulcanite piping. The 

 system it is proposed to use for keeping the sea-water in 

 good condition is known as the "circulating system." It 

 was introduced into England by Mr. Lloyd, and is in use 

 at the Crystal Palace and, I believe, all the inland aqua- 

 riums. The Naples Zoological Station and various conti- 

 nental aquai'iums have also adopted this method of keeping 

 the water continually in a satisfactory condition. 



The system is briefly as follows : — By means of pumps 

 the water is forced from the reservoirs through vulcanite 

 pipes into the tanks. The pipes are placed about 2 feet 

 above the level of the water in the tanks, and the water is 

 forced through nozzles, the bore of which is from, say, one 

 eighth to one quarter inch diameter, and regulated with a 

 tap. Jets of water are thus forced into the tanks from some 

 little distance above, and air in a state of very fine division 

 is carried by the jet deep into the water of the tank, and 

 distributed through it. By this means all decomposing 

 organic matter is oxidised and the water constantly kept 

 in a condition satisfactory for maintaining life. The force 

 of the jet of water is regulated by the speed of the pumps 

 and by valves placed in the main pipes, according to the 

 amount of aeration required. The water overflows from 

 the tanks into so-called " circulating reservoirs," which are 

 placed below them but above the level of the water in the 

 main reservoirs, and through these it is conducted to a 

 culvert (Plate I, p) which conveys it back again to the main 

 reservoirs, to be again pumped up into the tanks. 



This is not the place to enter into a discussion of the 

 relative value of the various methods now in use for keep- 

 ing aquaria in good condition, but I would point out that 

 the advantage of the method adopted by the Association is 

 that the water is kept constantly in good condition. 



A series of nine tanks are placed along the whole length 



