said inside end of each of said pole pieces being a concave, curved, inside cylindrical surface which is shaped and sized to conformingly mate with {HEAD ~ said outside surface} of {TAIL ~ said ferrous cylindrical wall}, 
of
said inside end of each of said pole pieces being a concave , curved , inside cylindrical surface which is shaped and sized to conformingly mate with { HEAD ~ said outside surface } of { TAIL ~ said ferrous cylindrical wall } ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH