The Vault is Slate’s history blog. Like us on Facebook, follow us on Twitter @slatevault, and find us on Tumblr. Find out more about what this space is all about here. Between the advent of railway ...

His most recent show, about the image that rules public radio—the broadcast clock—can be played below. Or keep reading to learn more about the tool that keeps Robert Siegel and his brethren in check.

It’s called About-Time, it’s by RISD grad and Fulbright scholar Louie Rigano, and it eschews directional clock hands entirely for what we guess you’d call clock blobs — primary-colored circles that ...