I'm afraid that Northrup's book is just a bit too expensive for me but I 
would like to have a look at some photos of Twain at Saranac.  Actually, 
I received a query from a visitor to Twain's Geography regarding photos 
from a family photo album he has.  He is of the family of Seth Thomas, 
the famous watch-maker, and has an album of the family vacationing in 
the area.  There is a gentleman in some of the photos that look like 
Twain and I would like to compare them.  I don't believe there is a 
match but the only shot of Mark Twain I've seen is a thumbnail for 
promoting "With Pen and Camera".

/Unaffiliated Geographer and Twain aficionado/