The Phosphor Signal Lantern

Overview

Mountain villages in the Kessel valley had no telegraph line in 1902, and the nearest one was a day's walk away. Margit Ollander, a schoolteacher and amateur chemist, proposed a cheaper answer: lanterns that charged themselves in the sun and flashed messages from ridge to ridge at night, without oil or wire.

With funding from a small cooperative that called itself the Kessel Valley Signal Company, she built eleven lanterns and placed them on hilltops between six villages. On clear nights, a message could cross nine kilometres in a few minutes.

How it worked

Each lantern held a cylinder of glass coated on the inside with a phosphorescent paint of Ollander's own recipe. During the day, the cylinder sat in a mirrored box that concentrated sunlight onto it. At dusk, the operator closed the box and opened a glow-shutter, a set of blackened slats that could be flicked open and shut with a lever.

Messages used a simple code of long and short glows. The phosphor faded steadily through the night, so the first messages after sunset were the brightest and the easiest to read, and operators learned to send the most important news early. By two in the morning, the light was too weak to see beyond the next hill.

The lanterns also needed people. Every ridge had a volunteer keeper, usually a farmer's child, who opened the mirrored box at sunrise and sat with the lever after dark. Keepers were paid in eggs and candles, and the cooperative's records show that the most reliable station was run by two sisters who never missed a night in four years.

Why it disappeared

Cloudy days were the first problem: a lantern that had not seen the sun could not speak at night, and the valley had many cloudy days. The second problem was the paint itself, which turned brown after a few months and had to be scraped and reapplied by hand.

When a telegraph line finally reached the valley in 1909, the cooperative dissolved. Ollander continued to experiment with phosphors for several years and later published a short book on luminous paints for watch dials.

What survives

One lantern, without its glass, hangs in the village hall of the highest settlement. Older residents still remember their grandparents describing the soft green flashes on the ridges, and some say that the code survived as a game children played with torches long after the lanterns were gone.