Explanatory 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 

 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- C. 

 October 1952 



