阅读下面一首宋诗，然后回答问题。
                                                                                          宿云梦馆
                                                                                             欧阳修
                                                                     北雁来时岁欲昏，私书归梦杳难分。
                                                                     井桐叶落池荷尽，一夜西窗雨不闻。
                                         【注】欧阳修曾坐“朋党”之罪出放外任，这诗是外放时途经云梦驿馆之作。