Question

Read the sentence below and answer the following question:

During the whole of a dull, dark, and soundless day in the autumn of the year, when the clouds hung oppressively low in the heavens, I had been passing alone, on horseback, through a singularly dreary tract of country, and at length found myself, as the shades of the evening drew on, within view of the melancholy House of Usher. —Poe, "The Fall of the House of Usher"

Which of the following is true about the author’s syntax in this passage?