{TAIL ~ a ferrous well tube} comprising a hollow core which has {HEAD ~ a ferrous cylindrical wall} which is coaxial with and concentrically inside said surrounding ferrous cylindrical case, said magnets, and said pole pieces, 
{ TAIL ~ a ferrous well tube } comprising a hollow core which has { HEAD ~ a ferrous cylindrical wall } which is coaxial with and concentrically inside said surrounding ferrous cylindrical case , said magnets , and said pole pieces ,
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH