Glass deck prism, 2 3/4" wide x 3" high, available in cobalt blue, light green, cranberry, and turquoise.
In the days before electricity, light below a vessel's deck was limited to candles, oil and kerosene lamps. A clever solution for the light problem was the deck prism. Laid flush into the deck, the prism point drew light down below decks. This prism is an exact reproduction of Mystic Seaport's last remaining original Charles W. Morgan deck prism.