Expl&natory Note 



The series embodies results of investigations, usually of restricted 

 scope, intended to aid or direct management or utilization practices and 

 as guides for administrative or legislativs actiono It is issued in 

 limited quantities for the official use of Federal, Stace or ooopere.ting 

 agencies and in processed form for economy and to avoid delay in publication. 



Washington, D.C. 

 August, 1952 



