# What's this weird bit of glassware from the physics lab?
**URL:** https://boards.straightdope.com/t/whats-this-weird-bit-of-glassware-from-the-physics-lab/648960
**Category:** Factual Questions
**Created:** [January 31, 2013, 9:42pm UTC](https://boards.straightdope.com/t/whats-this-weird-bit-of-glassware-from-the-physics-lab/648960 "2013-01-31T21:42:52Z")
**Posts on this page:** 7
**Page:** 2
### Author:  [@allyn](https://boards.straightdope.com/u/allyn)
#### Post date: [February 1, 2013, 10:26am UTC](https://boards.straightdope.com/t/whats-this-weird-bit-of-glassware-from-the-physics-lab/648960/21 "2013-02-01T10:26:48Z")
Wikipedia’s entry on Geissler tubes:
[http://en.wikipedia.org/wiki/Geissler\_tube](http://en.wikipedia.org/wiki/Geissler_tube)
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### Author:  [@MrDibble](https://boards.straightdope.com/u/MrDibble)
#### Post date: [February 1, 2013, 12:47pm UTC](https://boards.straightdope.com/t/whats-this-weird-bit-of-glassware-from-the-physics-lab/648960/22 "2013-02-01T12:47:22Z")
> [@cmyk](#):
>
> Give the man a cigar!
>
> [Ohh, pretty.](http://www.neatorama.com/2008/06/27/the-cathode-ray-tube-site/)
Here’s a [direct link](http://www.crtsite.com/page6.html). Pretty is right.
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### Author:  [@naita](https://boards.straightdope.com/u/naita)
#### Post date: [February 1, 2013, 1:47pm UTC](https://boards.straightdope.com/t/whats-this-weird-bit-of-glassware-from-the-physics-lab/648960/23 "2013-02-01T13:47:19Z")
I fed it 5 kV with no prettiness appearing. ☹
If there’d been even a hint of light I’d have left it to heat up for a while, but there was absolutely no noticable anything. On to the next unidentified apparatus I guess …
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### Author:  [@AaronX](https://boards.straightdope.com/u/AaronX)
#### Post date: [February 1, 2013, 1:59pm UTC](https://boards.straightdope.com/t/whats-this-weird-bit-of-glassware-from-the-physics-lab/648960/24 "2013-02-01T13:59:18Z")
Don’t those things need to be struck? Try hooking it to a fluorescent ballast?
Or a camera flash circuit…
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### Author:  [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)
#### Post date: [February 1, 2013, 2:07pm UTC](https://boards.straightdope.com/t/whats-this-weird-bit-of-glassware-from-the-physics-lab/648960/25 "2013-02-01T14:07:56Z")
Ahhhhhhh, it’s a 1920’s style Death Ray.
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### Author:  [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)
#### Post date: [February 1, 2013, 5:01pm UTC](https://boards.straightdope.com/t/whats-this-weird-bit-of-glassware-from-the-physics-lab/648960/26 "2013-02-01T17:01:35Z")
How do some of those tubes ever turn on? Look at the one on the [top right](http://upload.wikimedia.org/wikipedia/commons/e/e7/Geissler_tubes_%28switched_on%29.jpg)of that Wikipedia page.
Once it’s _on_, the ionized gas acts more or less as a wire, and it’s stable with a voltage drop that follows the path of current. But when it’s off and you apply a voltage, the electric field mostly doesn’t point _along_ the tube at all. Even local ionization near the electrodes would be pulled towards the sides of the tube, and not always along it. In many places, it would be pointing opposite the direction it will point in its on state.
( **naita** ’s tube is roughly straight, so I can imagine that one turning on.)
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### Author:  [@naita](https://boards.straightdope.com/u/naita)
#### Post date: [February 4, 2013, 5:42pm UTC](https://boards.straightdope.com/t/whats-this-weird-bit-of-glassware-from-the-physics-lab/648960/27 "2013-02-04T17:42:38Z")
The tube where the electrons would flow is quite spirally actually.
I suspect the failure of the tube to light is due to the near vacuum failing over time due to imperfections where the electrodes enter the tube. It’s a pity I don’t have an easy way of both determining and fixing that.
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