请哪位英语高手帮我分析下这段话的句子结构及其作用（就是属于长句、短句或者别的之类的） 急啊!

请哪位英语高手帮我分析下这段话的句子结构及其作用（就是属于长句、短句或者别的之类的） 急啊!
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.