What Is a Deck Prism On Ships?

In the past, aboard the old sailing vessels, prisms were used to re-direct the sunlight to those areas in the vessel where sunlight never penetrated, generally below deck areas. As compared to oil and kerosene lanterns and even candles, desk prisms offered a much higher safety parameter, making them the first choice to be equipped onto the vessels’ decks.

According to available records, it is said that the usage of these ship lights started at around the 1840s.

Deck Prism on ship

However, even as many validate this era as the vogue period for prism decks, many argue that the equipment’s usage started much earlier, perhaps centuries afore.

What were the important features of Deck Prism?

  • The deck prism was generally built of glass, like any other conventional prism
  • The prism deck was mounted on a roof, where sunlight could be best reflected or on a holding device
  • Sailing vessels, at times, had more than one deck prisms mounted for better lighting
  • The deck prism used to be flat-bottomed, making it easy to mount it, while tapering at its top while having a lot of faces for the light to be reflected

While most prisms used to be orbital and flat-bottomed, there were some prisms which were rectangular and flat-bottomed in nature. One of the most famous vessels with prisms shedding ship light was the American whaling vessel Charles W. Morgan.

The vessel operated during the early-1840s, has been re-modelled presently and placed in the Mystic Seaport repository, while the prism equipped on it has also been imitated and made available throughout the world.

Apart from its usage in general vessels, the deck prism was also used for vessels carrying coal. In these vessels, the reflected light used to indicate the actual quantity of the coal cargo contained within them.

Many maritime repositories contain artefacts of this particular nautical equipment. In the present times, while modern electronic gadgets have made availability of light easy, the singularity of these past amenities cannot be forgotten. This is why perhaps many vessels still affix a prism deck, to enable one reconnect with a much-needed maritime history.

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  1. I never knew what a prism ship was until just now researching it even though I had heard the phrase decades ago as a kid in the song in the court of the Crimson King by King Crimson when it first came out . I’ve actually seen those in some antique shops … not knowing what they were for originally .

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