Compare Letters 3, p. 363 n. 3, which dates their acquaintance from 14
August
1869: "Among the 'good boys' on the *Courier* was its co-editor, poet David
Gray (1836-88), who became one of Clemens's closest Buffalo friends."  In
Letters 4, the index lists several dozen page references to Gray, including
a
main entry at p. 102 n. 9. Clemens later recalled that Gray became an
"intimate
friend through his intimacy and mine with John Hay" (L4, 292 n. 3).