At the end of five years he was transferred to Prank” 
ford Arsenal , Phi lade Iphia , and thense to Washington, Do C® 
Being cut off from immediate contact with steel, his thoughts 
concentrated upon geology, especially upon the physical side 
of the subject* He became a member of the Philosophical 
Society of Washington in 1672, and became acquainted with 
Professor Henry and Professor Baird, who took great interest 
in him* .through the former and Major Powell he was induced 
to consent to a detail for duty with the Powell Survey, 
beginning May 15, 1675* 
