Why Tenure is Necessary

From the Chronicle of Higher Education:

It’s fair to say that Henry Petroski loves old objects. Mr. Petroski, a professor of civil engineering and history at Duke University, has written about forks and zippers, paper clips and pencils. His latest book is a history of an extremely primitive tool: the toothpick.

That book would be The Toothpick: Technology and Culture, released this past October.

I wonder if he took a sabbatical to write it?

Read more here, if any.