This paper was chosen as one of the top 100 papers in the National Institute of Science and Technology's first 100 years. It was published in the U.S. government publication "A Century of Excellence in Measurements, Standards, and Technology 1901-2000." The author, Dr. Estal Dale West, was inducted in the NIST Portrait Gallery of Distinguished Scientists, Engineers and Administrators in Gaithersburg, Md. in 2002.