Salute to historian Crosby

Jim Rossi’s discussion of my book, “1491” (Book Review, Aug. 21), claims that it “owes a greater debt than [I] acknowledge” to Alfred W. Crosby’s classic, “The Columbian Exchange.” Although I quote Crosby a dozen times and laud its importance in my bibliography, I wholeheartedly endorse Rossi’s charge. “The Columbian Exchange” so changed our conception of what history is about that it is practically impossible to fully acknowledge its impact. In print more than 30 years, it remains a pleasure to read -- if only all historians wrote as well!

CHARLES C. MANN

Amherst, Mass.