Explanatory Note 



The series embodies results of investigations usually of 

 restricted scope, intended to aid or direct management or utili- 

 zation practices and as guides for administrative or legislative 

 action. It is issued in limited quantities for the official use 

 of Federal, State or cooperating agencies and in processed form 

 for economy and to avoid delay in publicationo 



Washington, D,C< 

 May, 1952 



