1. The lower course of the river Niger, as far as it was ascended in the expedition under Captain Trotter, R.N., 1841 Yale Public content 1848. 2016-01-29T16:21:07Z. 2016-07-16T21:14:04Z. John Arrowsmith, 10 Soho Square. English. cartographic image. Public. Niger River, Niger River Valley, and Africa, West.