You might take a look at Branch's *Clemens of the Call*.  He reprints many
of the articles Twain wrote...I don't recall if the collection includes
anything on O"Byrne. Best of luck.
        Jan McIntire-Strasburg

On Sun, 9 Nov 1997, Barbara Schmidt wrote:

> In a letter to the Territorial Enterprise dated Feb. 5, 1868
> and  printed on March 1, 1868 Twain writes a very colorful column
> about meeting on the street of Broadway in New York a picturesque
> character/con artist/journalist/Fenian named Felix O'Byrne --
> someone he had known from his days in San Francisco.  According to
> Twain, Felix "said he had always remembered me for saying a merciful
> word in print for him when he was being sorely hunted by the press of
> San Francisco."
>
> Does the earlier Twain writing related to Felix O'Byrne survive
> in any collection of his San Francisco writing?
>
> Barb
>