JSTOR, the major supplier of scholarly journal runs is beginning a service of providing public domain journals to any web user for free. I checked their initial release and found considerable Twain content here already - 

http://www.jstor.org/action/doAdvancedSearch?q0=Mark+Twain&f0=au&c1=AND&q1=&f1=au&acc=on&Search=Search&sd=&ed=&la=&jo=

Sometimes long URLs get broken up in email, so if the end of the above is not underlined, just copy/paste the entire string into your browser.

Here is more information about the project:

http://about.jstor.org/participate-jstor/individuals/early-journal-content

Given JSTOR's reputation for quality and thoroughness, this is fantastic news. Enjoy!

Terry

Terry Ballard
Assistant Director of Technical Services for Library Systems
New York Law School, Mendik Library
185 W. Broadway
New York, NY, 10013
Telephone: 212-431-2106
Web: www.terryballard.org
Blog: librariansonedge.blogspot.com
Tweets: twitter.com/terryballard