said {HEAD ~ ferrous cylindrical wall} having an outside surface, {TAIL ~ an inside surface}, and a central axis, said outside surface being a convex, curved, outside cylindrical surface, said outside surface being contiguous said inside ends of said pole pieces, 
said { HEAD ~ ferrous cylindrical wall } having an outside surface , { TAIL ~ an inside surface } , and a central axis , said outside surface being a convex , curved , outside cylindrical surface , said outside surface being contiguous said inside ends of said pole pieces ,
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL 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 OTH OTH OTH OTH OTH