E-MAIL MAY HAVE CHANGED THE WAY WE CORRESPOND BUT IT HASN'T CHANGED HUMAN NATURE.

In the preface to the 1979 edition of his cultural study of the martini, the classicist Lowell Edmunds acknowledged the help of numerous people. He also noted having discovered "a law of correspondence," which he stated as follows: "In both the academic and the business worlds, the more important the person, the sooner he or she answers a letter."

As if stating a corollary, Edmunds continued, "assistant professors are the only ones who do not answer their mail at all; associate professors are prompter, professors still prompter, and deans the promptest of all," at least with off-campus correspondence. In my experience, Edmunds's law and corollary ring true.

When I was a graduate student submitting my first paper to the top journal in my field, I was greatly impressed that its editor wrote back to me within days. Subsequent correspondence with him revealed that, even when traveling abroad, he had his mail forwarded and responded promptly.

Soon, however, I encountered what might have appeared to be a counterexample. As a new assistant professor, I found myself sitting in the office of my division head when his mail was brought in. As we continued our conversation, he proceeded to open letters and made a show of tossing them half-read into the wastebasket.

In retrospect, I realize his behavior did not contradict Edmunds's law after all. The division head, who had been department head, retained little power beyond that of intimidating young faculty members. Rather than encouraging them to reach out to the senior colleagues in their field, he made them wonder if writing letters was worth the effort.

Though actions like his may explain why some assistant professors were reluctant to send out unsolicited letters, what could explain Edmunds's experience that they did not answer mail that requests a reply? Perhaps it had something to do with the unrefereed nature of correspondence.

There is no opprobrium associated with submitting an imperfect manuscript for publication. Grammatical errors, misspellings, typos, and even more serious flaws give referees something to comment upon, and their help can be acknowledged in print. A letter, however, once sent seldom can be revised. The writer has only one chance to get it right, and assistant professors are notoriously fearful of getting it wrong.

In the 25 years since the first edition of Edmunds's book, the art of correspondence has of course been revolutionized. Instead of arriving on sheets of white paper, which can be tossed, communications now come from out of the blue as electronic messages, which can be deleted.

In the meantime, a revised edition of Edmunds's book appeared, but in the new (1997) preface he puts forth no new laws. In fact, e-mail knows few constraints and promotes fewer inhibitions. From the start, it was no disgrace to use sentence fragments, idiosyncratic spelling, or bizarre formats. As a result, it seems, no one should be intimidated in sending a message to anyone, and no one should have to agonize over the formality of a response.

However, I still detect a hint of Edmunds's law of correspondence at play. People who have a penchant for achievement tend not to accumulate a backlog of undone tasks. Though their schedule may limit their time online, they often respond immediately upon opening an e-mail message. Those who read e-mail continuously may put off responding simply to conceal their accessibility. Though certainly I generalize, I beg the curious to forego testing the particulars of my own corresponding practices.

Henry Petroski is the Aleksandar S. Vesic Professor of Civil Engineering and a professor of history at Duke University. His latest book, Pushing the Limits: New Adventures in Engineering, was published in September.