Sentence:  A <WSD>century</WSD> ago , Newman saw that liberalism ( what we now might call secularism ) would gradually but definitely make its mark on English Protestantism , and that even high Anglicanism would someday no longer be a `` serviceable breakwater against doctrinal errors more fundamental than its own '' . 
Meaning of the word marked with <WSD> tags:  a period of 100 years