Perhaps out of time . . but I started only 5 months ago some research work about this branch of the family. 1)there's a book about Alexander Bryan JOHNSON (1786-1867), grandson-in-law of Pres. ADAMS, and consequently brother-in-law of Susan (am I wrong ?), some anecdotes with her are reported in : "Alexander Bryan JOHNSON, philosophical Banker", by Charles L. Todd & Robert SONKIN, Syracuse Univ. 1977, 978-0-815621-88-4, should still possible to be bought on internet. 2) also see "A guide to the family JOHNSON papers 1776-1937" athttp://rmc.library.cornell.edu/ead/htmldocs/RMM04928.htmlhttp://rmc.library.cornell.edu/ead/htmldocs/RMM04928.html
I came on that way because I'm a direct descendant of Solomon JONES (1782-1853) from LONDON, in turn direct cousin of Alexander B. JOHNSON, they were corresponding sometimes with each other !