Explanatory Note 



The series embodies results of investig^ations, usually of restricted 

 scope, 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 cooperative 

 agencies and in n recessed form for economy and to avoid delay in publication. 



Washington, D.C. 

 February, 1952 



