The Magic in the Glass
Though I didn’t know it for many years, a Fresnel lens was a fixture in my childhood. I grew up visiting Cambria, California, a small coastal town known for its coastal boardwalk, its elephant seal rookery, and its proximity to Hearst Castle. For me, it was my home away from home.
Every year, my parents took me to the Pinedorado, a Labor Day festival that Cambria has hosted for 70 years. Rather than focusing on the parade or the carnival games, I was interested in the glass room planted in front of the Pinedorado Grounds like Willy Wonka’s glass elevator. There was a strange ornament behind the glass — something out of a Ray Bradbury novel. I remember staring at the prisms, trying to understand how they caught errant beams of sunlight.
As it turns out, the ornament in the glass room is a first-order Fresnel lens. It consists of over 1,000 prisms, all of which were hand-crafted in France in the 19th century. The lens stretches 9 feet tall and six feet wide, weighing almost 13,000 pounds. Adjusted for inflation, a jewel of that scale would cost nearly $400,000.
Why were these colossal ornaments made? Were they worth it?
Some History
We may perceive Fresnel lenses as a bygone technology, but they were an absolute necessity for an economy dependent on maritime trade. During its fledgling years, the United States relied on imports from foreign nations. But sending cargo across the Atlantic was not a risk-free endeavor. With strong currents, rocky shores, and limited visibility, docking a vessel safely was nearly impossible. Hence the need for lighthouses.
Lighthouses were high on the priority list for early America. Congress’ 9th Act transferred the nation’s 12 existing lighthouses into federal control, creating a ragtag lighthouse board. Our founding fathers even took an interest in lighthouse-related affairs. George Washington increased the annual wage of the American lighthouse keeper from $120 to $333.33, and Thomas Jefferson personally presided over the hiring of specific keepers.
While there was a strong need for lighthouses, they weren’t all that effective before the advent of the Fresnel lens. The lighthouses of the 1600s were large fire pits that could scarcely be seen from the ocean. The beacons got more sophisticated with the reflecting model, which consisted of an oil lamp backed by mirrors. Still, these lost 83% of their luminosity. The inefficiencies of these lighthouses all boils down to one central aspect of light: it’s erratic. As one of my characters says in my book, “it doesn’t know how to point.” Because light shoots in virtually every direction, it isn’t equipped to travel great distances.
In the early 1800s, a French scientist named Augustin Fresnel decided to correct the erratic nature of light. Rather than increasing brightness or luminosity, he decided to improve its economy.
His lens used reflection and refraction to bend rays from a light source in a single direction. Though the light doesn’t appear that strong, it’s remarkably efficient, losing only 17% of its luminosity. A beam of light can travel over 20 miles after passing through a Fresnel lens — well beyond the curve of the horizon.
https://www.ponceinlet.org/Understanding-how-Lighthouse-Lenses-Work-1-6297.html
After the Fresnel Lens was introduced in 1822, the world was eager to implement the technology. From 1800 — 1899, the number of lighthouses in the United States exploded from 24 to over 850. This spawned a new, demanding vocation that brought lighthouse keepers to some of the most rugged corners of the world.
It has been estimated that Fresnel lenses and lighthouse keepers saved over one million shipwrecks throughout the 19th century.
Theme for a Novel
Once I started educating myself on the history and the optics of the Fresnel lens, I couldn’t cast aside its poignancy. I was compelled by the idea of increasing luminosity not by intensifying the light source, but by improving its economy. Light, by its nature, is chaotic and inefficient. It’s up to us to channel it in a single direction; otherwise, it won’t be seen.
Recently, I read a message on a teabag that read as follows: “It is the light in the lantern which shows you the path, not the lantern.”
The Fresnel lens insists on just the opposite. It isn’t the raw flame that determines how far light can travel; it’s the lens surrounding it.
The magic is in the glass.