100 DESCRIPTION OF THE LABORATOEY AT PLYMOUTH. 



of the soutli wall of the aquarium. They are all 4 ft. wide 

 and 4 ft. deep. One of them {Jc) is 15 ft. long, two (l I) are 

 10 ft. long, and the remaining six (j) are 5 ft. long. The cir- 

 culating reservoir below this row of tanks is 2 ft. 6 in. wide 

 and 3 ft. 6 in. deep. The circulating reservoirs are built of 

 concrete and brickwork, and the internal surface covei'ed 

 with a special asphalte. The tanks are supported on the 

 walls of the circulating reservoirs ; each tank is provided 

 with an overflow into the circulating reservoir and an over- 

 flow into the tank next to it, the level of the tanks being 

 so arranged that the water flows from east to west. These 

 overflows are so arranged that they can be used or not as 

 desired, and thus any tank can be isolated. 



A second series of three tanks is placed along the north 

 wall. Two of them are 5 ft. deep and 9 ft. wide, one of 

 these (/) being 15 ft. 6 in. long, the other (g) 30 ft. 6 in. 

 long, while the third (h) is 5 ft. deep, 5 ft. wide, and 15 ft. 

 long. The circulating reservoirs below are 3 ft. 6 in. deep 

 and 7 ft. wide. The overflows are arranged like those on the 

 south side. The height of the top of these tanks from the 

 floor is 7 ft,, while on the south side the top of the tanks is 

 6 ft. 6 in. above the floor level. 



A third series (e) of five "table tanks," each 9 ft. 9 in. 

 long, 2 ft. 3 in. wide, and 1 ft. 9 in. deep, is placed down the 

 centre of the room. They are supported upon the walls of 

 a circulating reservoir 1 ft. wide and 3 ft. deep, and being 

 only 4 ft. above the floor level their contents can be exa- 

 mined from above. 



The water in each of the circulating reservoirs flows at 

 the west end into a culvert (^:») which conducts it back to the 

 main reservoir ; the culvert is of concrete, lined with 

 asphalte, and covered over with slate. 



It will be convenient to include in this description of the 

 aquarium a series of twelve small tanks, which are placed 

 in a double row in the main laboratory (Plate II, k) . They 

 are supplied by the pumps with water, which flows again 

 into the main reservoir. Each of these tanks is 1 ft. 6 in. 

 deep, 2 ft. 3 in. wide, and 5 ft, long. The pipes are of vul- 

 canite. A supply of water is also conducted through pipes 



