Dissonance: Noun

Definition: lack of agreement; especially    :  inconsistency between the beliefs one holds or between one’s actions and one’s beliefs

In the essay “The Brooklyn Bridge” by Philip Lopate, the author stated ” It was this very dissonance of sleek steel and old fashioned granite that annoyed Montgomery Schuyler…”

Source: http://www.merriam-webster.com/dictionary/analogy?show=0&t=1387250842

Now that understand the word I know it meant that this disagreement was the cause that Montgomery Schuyler became annoyed.