MARINE AQUARIUM PROCEDURES AND TECHNIQUES 



67 



edges that recede according to Garnaud's 

 principle of the tank with nonparallel 

 sides, and with plate glass inclined at about 

 20° from the vertical so as to show the 

 sand bottom at a convenient angle. The 

 back of the tank (the part opposite the 

 glass) will be strongly concave and very 

 much bell-mouthed. In this section, the 

 wall will be inclined at about 45°. Under 

 these conditions, an observer looking 

 through the glass will not see the lateral 

 edges ; he will practically not see the water 

 surface, and he will easily confuse tlie 

 back and the floor. 



The principle of the aquarium with 

 nonparallel sides according to Garnaud 

 has one fault : it presents to the public an 

 exhibit area that is relatively small as 

 compared with the size of the tank, and if 

 the exhibit is particularly attractive the 

 visitors will crowd each other in front of 

 the aquarium. Consequently, we suggest 

 an entirely new form in which two sides 

 are slanted parallelepipeds that enable the 

 visitors to see the exhibit clearly from two 

 angles. The advantage in servicing the 

 aquarium is certain : despite the large size 

 of the tanks, they have very little depth 

 (fig. 10, 11, and 12). 



Figure 10. — Sand tank for public exhibit. The 

 heavily stippled areas represent the blind sides 

 of the tank. Sand fills the lower section (B) 

 of the entire tank, up to the bottom edge of 

 the plate glass (A and A'). The back of the 

 tank (D) slopes backward in order to blend 

 visually into the sandy soil bottom. E is the 

 channeled corner holding the plate glass. 



Figure 11. — Bird's-eye view of sand tank for 

 public exhibit, showing 5-sided shape of tank. 



Figure 12. — Cross section through the middle of 

 the sand tank, from E at center front to D 

 at back. 



An aquarium of this type, in which the 

 length of the two panes of glass reaches 2 

 m. while its total length amounts to 2.50 

 m. and its width is 1.60 m., affords a field 

 of view that appears to be unlimited. In 

 this example, the height of the free water 

 would certainly not exceed 1 m. 



Cultivation of algae 



This arrangement is very efficient for 

 cultivating marine algae, either for par- 

 ticular studies or for maintaining an iso- 

 lated marine environment in perfect 

 equilibrium (figs. 13 and 14). 



We have developed a technique of cul- 

 ture upon a film of water. Under these 



