In late 1889 he went to the University of Bologna , where he worked for the rest of his life on things like the Zeeman Effect , ` Roentgen rays ' , and magnetism . Towards the end of 1889 he was called to the University of Bologna , his home city , where he worked for the rest of his life on subjects such as the Zeeman Effect , ` Roentgen rays ' , magnetism and the results of Michelson 's experiments .