[I've been
reading]
A Short Bright Flash

A history of the Fresnel lens and lighthouses generally. Picked this up when I was idly browsing library shelves and it was much more interesting than I expected. French engineers! Civil War lighthouse attacks! World War II German lighthouse occupiers! Did you know that many Fresnel lenses floated in vats of mercury and this is believed to be why lighthouse keepers have a reputation for being drunk and/or crazy? Read this book, learn more.