River Nith is a river that is located in the southwest of Scotland; it is one of the major rivers of Scotland and flows nearly twelve miles. It is mentioned in the excerpt from Recollections of a Tour Made in Scotland, in which Dorothy writes of traveling alongside it. They corss the river and comment on the land surrounding it, a significant part in her commentary on Scotland. As a major Scottish river, it is fitting that it is a large part of their travels. 

"Travelled through the vale of Nith, here little like a vale, it is so broad, with irregular hills rising up on each side, in outline resembling the old-fashioned valances of a bed. There is a great deal of arable land; the corn ripe; trees here and there—plantations, clumps, coppices, and a newness in everything. So much of the gorse and broom rooted out that you wonder why it is not all gone, and yet there seems to be almost as much gorse and broom as corn; and they grow one among another you know not how. Crossed the Nith; the vale becomes narrow, and very pleasant; cornfields, green hills, clay cottages; the river’s bed rocky, with woody banks. Left the Nith about a mile and a half, and reached Brownhill, a lonely inn, where we slept" (Wordsworth). 

https://en.m.wikipedia.org/wiki/File:The_River_Nith,_Dumfries_(7381585944)_(2).jpg

https://newcumnockhistory.com/2012/04/29/place-name-river-nith/