The letter was written by Darwin to thank an American geologist, Dr. Ferdinand Vandeveer Hayden, for sending him copies of his research into the geology of the region that would become Yellowstone National Park.
达尔文写这封信是为了感谢美国的一位地质学家费迪南德·范德维尔·海登博士,感谢他给了自己一个区域地质研究的复印件,该区域后来成为黄石公园。