CALIBRATION TANK 



The main tank is rectangular. Its internal 

 dimensions are 28 by 24 by 31 inches, and its capacity is 

 70 gallons. It is supported 2-1/2 feet above the floor by 

 upright aluminum pipes mounted at its corners. It is 

 insulated on all sides with cork, 4-1/2 inches thick, backed 

 by sheets of .waterproof plywood. The inner liner is con- 

 structed of Type 304 stainless steel, the front panel being 

 1/2 inch thick and the bottom and other three sides being 

 3/32 inch thick. The front panel supports the glass panes' 

 for two lighting ports and furnishes rigid backing for the 

 centrally located viewing window which is clamped against 

 it and sealed with an "O" ring. All edges are welded. The 

 original liner, constructed of Lucite sheets glued at their 

 edges, was discarded because it deteriorated in the pre- 

 sence of the 25 -percent solution of ethyl alcohol (used to 

 prevent freezing and to control growth of algae). 



LIFTING CABLE 



SUPPORT LEG 



GUIDE ROLLERS 



CALIBRATION 

 TANK 



CONTROL PANEL 



ELAPSED 

 TIME METER 



SWITCHES 



READING 

 TELESCOPE 



Figure 1 . Calibration tank with control panel. 



