Interview with astronomer Clyde Tombaugh, discoverer of Pluto

Although Pluto has been demoted from an ordinary planet to a "dwarf planet," Americans are rightly proud of its extraordinary discovery in 1930 by astronomer Clyde Tombaugh at the Lowell Observatory near Flagstaff, Arizona.  Fifteen years ago, shortly after his 90th birthday, I had the opportunity to interview Tombaugh by phone.  I've posted the interview on the Philadelphia Area Center for the History of Science (PACHS) site (where I am now one of the contributing bloggers):

Interview with Clyde Tombaugh