Gossamer: Noun

Definition: a very light or delicate material

In the essay ” The Brooklyn Bridge the author uses this word to describe the Brooklyn Bridge. ” The Brooklyn Bridge  is more endearing… like granite and gossamer.”

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

Now that I know the meaning of this word I understand the author was referring to the bridge as a place that is strong but at the same time very delicate.