It is an old saw among editors that the most likely place to make an error is in a headline, a place so obvious that the critical eye can glide over it, as if unable to believe that mistakes could possibly turn up in large type. In two recent issues we fell into this trap. In the subhead to Alfred Kazin’s “Where Would Emerson Find His Scholar Now?” (December 1987), the date should have read 150 years later, not 175. And in “The Time Machine” for February 1988, the year 1588 should have been followed by the words Four Hundred Years Ago.