The article about the gold-bearing springs sounds like a reprinting
of a letter to the editor of the New York _Evening Post_, written by
Mark Twain and published on 16 September 1880.  See "Millions In It,"
pp. 761-762 in Louis J. Budd, ed., _Mark Twain: Collected Tales,
Sketches, Speeches, and Essays, 1852-1890_ (New York: Library of
America, 1992) and Budd's notes to the text.  Although the Budd reprint
places the letter as being written by SLC at Hartford, Paul Machlis'
_Union Catalog of Clemens Letters_ (Berkeley: U of California Press,
1986) places it at Elmira, and dates it 14 September 1880 (MTP reference
01833).

Taylor Roberts
University of British Columbia