4. Artificial lights no detriment. 



5. Entrapped air does permeate all areas of ladders o The entrapped air 

 appears in the shape of rather large air bubbles, very different than sur- 

 face conditions would indicate. 



Continued obsej-vations during the coming year is anticipated. 



/s/ F. A. 



F. L. Abbott 

 "U.S. Engineer office 

 Oct 14 8 25 AM '46 

 Portland, Oregon" 



35 



