Bottom can , — The bottom can, approximately 12 inches in diameter 

 by 13 inches high, is essentially a reservoir for holding a measured 

 volume of water. Connected to the bottom of the can is a pipe. By 

 means of rubber tubing, this pipe leads to a piece of glass tubing that 

 is held by clips on to a support fastened firmly to the can and that is 

 used as a gauge to determine changes in the volume of water contained 

 in the can. 



In figure 10, this glass tubing is shown protruding at an angle 

 from the lower right side of the picture. This tube will indicate a 

 change of 60 cubic inches in the volume of water. It slopes upward 

 with a rise of 1 inch in 10 horizontal inches, which slope permits a 

 sensitive reading of any change in the volume. The midpoint of the 

 tube corresponds to a height of water in the can of about 9 inches. 



A scale for determining changes in the volume of water in the 

 can is made from a small strip of soft copper. The ends of the strip 

 are cut and bent into clips so that the scale can be hung on the glass 

 "tube and moved along as desired. Four calibrated reference lines are 

 scratched onto the scale. Additional lines are added and so spaced 

 that the scale covers 60 cubic inches and indicates major divisions 

 at each cubic inch of volume change in the main tank. 



Vibrations retard the reading of the gauge. The stand therefore 

 must be braced well and the tank bearing the gauge must be fastened 

 firmly to a heavy table. A small level is attached to the arm that 

 holds the gauge so any displacement of the gauge may be corrected. 



Middle can, -— The middle can is essentially a metal measuring 

 basket It is lH inches high and 10-1/2 inches in diameter. Serving 

 as the bottom is a heavy, 1/U-inch thick iron plate, which has holes 

 bored in concentric circles, the radii of which differ consecutively 

 in length by l/2-inch* 



The basket contains two vertical slots cut into the opposite 

 sides in a sawtooth pattern with a tooth for every half inch of height. 

 By sighting across the teeth, one can estimate the height of a sponge 

 placed in the basket. 



Welded onto the side of the basket near the top are three sma ll 

 lugs. These lugs fit into slots cut into the upright supporting pipes 

 and permit the basket to travel up and down without rotating. The 

 upper ends of the slots are cut and widened in such a manner that by 

 a slight twist of the basket, the lugs have a support that enables the 

 basket to be held suspended in place in a "rest" position. 



Top can . — The top can is essentially a vessel for exerting pres- 

 sure on a sponge held in the middle can. This top can is li; inches 

 high and of such a diameter as to fit closely inside the middle can, 

 A loose handle is attached inside the top rim. The can is lifted up 

 and down by means of rope and pulleys attached to the top of the sup- 

 porting frame. The pressure exerted is variable by means of the 

 amount of water cc- number of weights placed in the can. 



38 



