"an unobstructed view of a lofty brick wall"
Usually, when "an unobstructed view" is used, the expectation is of a wide vista -- lots of beach and ocean or big sky and lots of mountains or something absolutely beautiful and huge like one of those.
Another way to look at is that the view is not unobstructed; the wall is obstructing whatever view might be out there.
However "an unobstructed view" of a wall within 10 feet of the window is the opposite of what one would expect!
What is the irony is this passage?
In that direction, my windows commanded an unobstructed view of a lofty brick wall, black by age and everlasting shade; which wall required no spy-glass to bring out its lurking beauties, but, for the benefit of all near-sighted spectators, was pushed up to within ten feet of my window panes.
Is t the Black all wit unexpected beauty? But I don't know what that means.
2 answers
The sentence is filled with verbal irony. If taken literally, the reader would think that the narrator enjoys the beauty of old, blackened brick walls, and is pleased that his window is so close to one as to afford him a good view. Identifying the use of verbal irony in this sentence allows the reader to understand that the narrator is actually disgruntled with the scene his window presents.