Explanatory Note 



The series embodies results of investigations, usually of 

 restricted scope 9 intended to aid or direct management or 

 utilization 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 publication.. 



Washington^, D. Co 

 May 1950 



