Explanatory Note 



The series embodies res'alts of investigations^, usually of 

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

 zation practices and as guides for administrative or legislative 

 actioHo It is issued in limited quantities for the official use 

 of Federal, State or cooperating agencjies and in processed form 

 for economy and to avoid delay in publication. 



Washington, D. C. 

 February 1953 



