I found several sites that mentioned "laylights" but did not give a clear idea of what they are. Please enlighten us.

What would a architect know about a wonderful historical building feature like a laylight? If it ain't titanium, they don't want to hear about it![/sarcasm]

A laylight is a decorative (stained glass or otherwise) window set into the ceiling of a room directly below a skylight. The sturdy skylight takes any load and the laylight is purely aesthetic. There is a wonderful set of laylights at the Vermont State House, one pane of which was literally shattered into hundreds of tiny pieces while the window was in storage. When the room was restored, a determined conservator pieced the entire thing together like a jigsaw puzzle (for which he didn't have a picture to guide him) and joined it all with epoxy. Now you can hardly tell which of the four panels was the broken one unless someone points it out.

F. Lander, Historic Preservationist