I'm fascinated by Fresnel lenses, those early 1800s inventions for lighthouses to spread light across the rocks and bays, warning ships of danger.

One small burner, a wick, in the center of the separated concentric circles of glass and held in place by bronze bars, could refract light so much farther than wicks burning behind magnifying globes and mirrors in days of lighthouse yore. 

How did Augustin Fresnel do it? Imagine an ordinary magnifying glass that has been sliced from the center domed area all the way to the back, then the slices put back together, but separated by a few inches. And this with early 19th Century tools!

There's a great article here for the history of how Fresnel worked with others to create the lens, and some great photographs of actual lenses, those now removed from lighthouses, replaced by airport beacons and modern technology.

A while back, I got to see my first large Fresnel lens up close. My friend Sandra and I enjoyed a Caravan Tour of Nova Scotia during leaf season, and in Halifax, we toured the Maritime Museum of the Atlantic. There it was, a huge Fresnel lens that once signaled the entrance to Halifax harbor.  Suspended from the ceiling, it was much taller than I. Mesmerized, I peered into its magic light, its crystal prisms, tiny rainbows everywhere.

The tinkle of a tune, my mother at the piano in church ... I hear the music, whisper the lyrics, still imprinted from the old red Methodist Hymnal of my youth. While others wander around me, I'm back in that little country church…

 Let the lower lights be burning!
Send a gleam across the wave!
Some poor fainting, struggling seaman
You may rescue, you may save.

One spot of light, refracted and magnified and sent out into the dark of night, as a warning, as a beacon, a welcoming home.

The light one makes, the words we speak and write, the magnification of our points of light.

There's a lesson here in this marvelous lens.

Note: Lyrics from "Let the Lower Lights Be Burning," written by Phillip B. Bliss in 1871. He also wrote "Almost Persuaded" and "Wonderful Words of Life," and other traditional gospel hymns. More on him at https://en.wikipedia.org/wiki/Philip_Bliss