How the hell do you "zoom in" on the dope sheet?

Okay, my eyes are not as good as they used to be. How do you “zoom in” on the dope sheet display? The mouse-wheel doesn’t make the display bigger or smaller – it seems to move along the timeline. (Blender 2.79b.)

User Preferences > Interface > Display > Scale

Or just hit S and move the mouse

uhh… yeah… (blush)