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Assume one constructed a submersible such as what Captain Nemo commanded, the Nautilus, and it had a useful depth of 1km. Using 19th century technology, what would they need to develop to allow functional and relatively practical exterior lighting? They intend to observe and explore the seabed near volcanic vents.

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  • $\begingroup$ Can we assume the presence/availability of plentiful air (as per the one on the story)? $\endgroup$ Aug 5 at 13:10
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    $\begingroup$ I am not sure I understand your problem:"Using 19th century technology, what would they need to develop to allow functional and relatively practical exterior lighting?" was answered by Edison light bulb in 1878 $\endgroup$
    – L.Dutch
    Aug 5 at 13:10
  • $\begingroup$ Edison's evacuated envelope would survive at that pressure with simple silica glass? $\endgroup$
    – Vogon Poet
    Aug 5 at 13:11
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    $\begingroup$ Radium! Its all the rage! $\endgroup$
    – Gillgamesh
    Aug 5 at 15:44
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    $\begingroup$ *"Edison's evacuated envelope would survive at that pressure with simple silica glass?" The light bulb by itself, maybe, maybe not. But anyway the lightbulb would be enclosed in a lamp, which can be made as strong as needed. The front glass of the lamp would be made exactly like the windows of the submarine itself. $\endgroup$
    – AlexP
    Aug 5 at 16:12

2 Answers 2

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Verne's divers (before their undocumented demise from caisson disease) used battery powered Ruhmkorff coils (auto-induction high voltage suppliers, similar to modern ignition coils) to provide high voltage for Crooke's tubes as portable lights (presumably with very heavy tube walls, perhaps of fused quartz). There's no reason these couldn't be made larger, powered by the boat's internal electrical system, and mounted in steerable reflectors for exterior lighting.

Mercury and sodium vapor lamps used in outdoor lighting until the 21st century (when LED replaced them) operate on the same principle, and have the same problem: the small number of bright emission lines makes color perception very inaccurate. With mercury arc, you can at least use a phosphor screen (excited by the UV) to provide a broader color spectrum (and this was known in the 19th century as well)

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  • $\begingroup$ But would it have worked? Has his fiction been tested in any way? I can not adopt his invention wholesale, as it would be a third party device. I suppose that is the problem. $\endgroup$
    – Vogon Poet
    Aug 5 at 14:38
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    $\begingroup$ Verne himself lifted this from real life. Ruhmkorff and Crookes were real people, and this was a real electric light that predated Edison's incandescent bulb by a couple decades. It lost because it needed high voltage (Edison didn't), and gas discharge destroyed color perception with its bright-line emission. Making them work under sea water at 100 atm. is "just" engineering. $\endgroup$
    – Zeiss Ikon
    Aug 5 at 14:44
  • $\begingroup$ Ummm, just put the contraption in a diving helmet? They have small viewport windows that the light could shine out of. $\endgroup$ Aug 5 at 15:47
  • $\begingroup$ @JustinThymetheSecond Still got effectively a vacuum inside the discharge tube. Either the helmet maintains 1 atm inside (and your divers are wearing J.I.M. type hard suits) or it doesn't and you still have the pressure, even without the water. $\endgroup$
    – Zeiss Ikon
    Aug 5 at 15:50
  • $\begingroup$ I believe the diving suits on the Nautilus were 1 atm. pressure inside the suit. The diving helmets were solid. bonhams.com/auction/21427/lot/266/… $\endgroup$ Aug 6 at 2:16
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The fundamental problems normal light bulbs would experience under high pressures combined with an incandescent or combustible light source are related to compressive and tensile forces acting on the casing and glass envelope. The casing can be made of any suitable metallic alloy available at the time, such as the brass used in diving helmets. But the glass will be subjected to unusual stresses. So the manufacturing process of that glass would have to evolve in a way that produces amorphous, crystal-free glass.

Arc furnace foundry

Getting the material to melt in a homogenous state, avoiding any crystalline inclusions, has been achieved using a furnace that employs an electric arc for its heat source. They would have to develop this technique, and also experiment with various metallic glasses. That had already been an art for the purpose of making rarefied glasses such as the Crookes tube that led to the discovery of X-rays.

High pressure quenching

The inventor needs to not only form the homogenous glass material amorphously, but they need to quench the glass at high pressure, which will further align the glass microstructure amorphously.

It is likely that you will only produce small lenses with this method, so the final lamp may be comprised of several compound windows in a convex honeycomb frame.

Honeycomb lamp configuration

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  • $\begingroup$ Just put it in a diving helmet? $\endgroup$ Aug 5 at 15:50
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    $\begingroup$ Trivia: In the 1930's William Bebe in the first bathysphere to go 1000 meters the glass window was 3 inches thick. I think I read some of the acrylic hulls for luxury submarines are about 300 mm thick (11.8 inches) but while rated for 1000m only dive to much shallower depths. $\endgroup$
    – UVphoton
    Aug 5 at 19:44

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