Measuring board . — In addition to the device described above, a 

 measuring board was used for determining the size of the sponges. This 

 board, which is shown in the lower left hand corner of figure 10, con- 

 sists of two boards, each of which is one foot square and is nailed at 

 right angles to the other. In addition, a vertical strip of aluminum 

 is nailed to the front of the base. The aluminum strip bears a half- 

 inch scalej the back vertical board bears horizontal lines marked in 

 divisions of one— half inch; and the bottom board bears concentric cir- 

 cles one-half inch apart. All scales are suitably numbered. 



Procedure used in water tests . — The following procedure is used 

 in the water tests: 



1. Fill the bottom "5an with water until the level in the slant- 

 ing glass tube reaches the midpoint, 



2. Blow gently into the end of the glass tube several times to 

 prevent any clinging of the water to the glass and resulting inaccuracy 

 in the determination of the level of water, 



3« If difficulty is encountered in determining the level, poke 

 a few grains of surface-active material, such as Dreft, into the tube 

 with a wire, 



U« Immerse the middle can, or measuring basket, in the water in 

 the bottom can to wet the measuring basket, 



$m lift the basket out of the water up to the rest position and 

 allow any water present to drain from the basket, 



6. Move the copper scale to indicate the starting level of water 

 in the can, 



7. Place a sponge in the basket and immerse the basket and sponge 

 in the water, 



8. Press the sponge against the bottom of the basket with a smooth 

 rod (not ha. id) until no more bubbles of air rise from the sponge, 



9. lift the basket from the water to the rest position and let 

 the free water drain back into the bottom can, 



10. Read the copper gauge to determine the volume of water absorbed 

 by the sponge and record this volume as USh, the water holding power, 



11, If the sponge is a Grass sponge, tip it on end, lean it against 

 the side of the basket to drain, and record the resulting final volume 

 as ¥ n t for the Grass sponge, 



12, Press the sponge well to remove water, and transfer the sponge 

 to the measuring board, 



13. Read the smallest and largest diameters of the sponge by means 

 of the circles on the bottom of the board. 



39 



