He thinkung and working ceaselessly until the end .
He left behind an enormous output of lithographs and writings , including books and articles on painting and lithography and 12 volumes of journals documenting his experiments in print - making .
Thinking and working ceaselessly until the end , he left behind an enormous output of lithographs and writings , including books and articles on painting and lithography and 12 volumes of journals documenting his experiments in print - making .