Technique

Thomas Frost in a letter to the New York Tribune, dated 14 February 1889, wrote:

'I observed only three straight lines in foreground - I should say, the bottom of the paper, and a little flake white which apparently had been spat upon the "distance."… [a] blot of burnt umber to the north ...'. 1

This does not help to identify it, nor add much to an understanding of the technique!