Call for Assistance

Can you help identify these items from the Museum archive?  They are listed as a pair of measuring tubes, a Wilson’s cloud chamber and a spectroscope.  What were they used for?


The second is a teaching aid – it demonstrated the principles of a cathode ray tube (as per an old TV). The electrons pass across the vacuum tube and are deflected by the magnetic field created by the two circular electromagnets. Not sure why the submarine museum has one – I would give it to a local senior school.


Top item is an early form of breathalyser used to detect leakage of rum from the Coxn’s store – usually found inside the Coxn or the 5th hand!
Cloud chambers were used to detect ionising particles – alpha, beta, & gamma rays (true dit). My guess is possibly useful in the early days of reactor design to determine effectiveness of shielding? But a crude implement for that purpose. Third items – bird feeders by the look of them! Tobs

Brian Thomas

Firstly I don’t think there is a Spectroscope or Spectrometer among the images. As the name suggests, a spectroscope splits a light source into its component parts. A rainbow does the job in nature but if you want to impress your grandchildren then an instrument to demonstrate the phenomenon can be constructed very simply. An oblong box with a slit at one end and a CD or DVD disk (plastic printed skin removed) inserted at an angle near the other end will serve. A viewing or camera hole set in the side opposite the disk reveals the makeup of a light source shone through the slit. The beam is split by the refraction effect from the laser cuts on the surface of the disk.

From the top:

Image 1. I can’t recall a Ringrose CO2 detector of that type, as Don Cleavin remembers, being deployed in boats from my time (A’s and O’s). I do seem to remember a combined unit or units capable of early warning for various gases but don’t quote me. Perhaps there is one such still in Alliance?

Image 2. When I looked up ‘Wilson Cloud Chamber’ it was quite a shock to learn something about radiation. Then I remembered Nuclear Defence exercises carried out on board HMS Decoy in the fifties. She was fitted with an overall spray system that was tested from time to time with the aim of washing away all those nasty particles. This process was followed up with white suited operatives toting radiation detectors taking great pleasure in frightening us with the consequences of radiation poisoning. Various types were mentioned including Alpha particles that freely pass through us every day. Again, YouTube is a source of many images from cloud chambers and it is scary to actually see tracks of particles that abound in our air space, including A particles.
A Cloud Chamber is an instrument that provides visual tracks of ionizing radiation passing through a super-saturated medium usually water vapour or alcohol. A charged particle creates a trail of ionized gas particles that reacts with the vapour to produce tiny droplets visible to the eye. The vapour has to be in a super-saturated condition. Depending on the solution, this condition can be achieved in various ways mainly by creating a temperature change or by increasing the pressure within the chamber. shipm4te is probably right about the CRT demonstrator as I can’t make out from the photograph a means of changing the pressure inside the glass. In other respects it could fit as a Wilson Cloud Chamber. The electro-magnetic rings fit also. Apparently a magnetic field acting on ionized particles within a chamber cause them to curve in a way specific to the type of particle. Identification and measurement is therefore easier.

Image 3. The pair of measuring tubes are a mystery. I posed the question to a neighbour who worked as a Lab. Assistant at Exeter University. His blank face said it all. Could they have something to do with humidity measurement? Dry wood chips in one tube could be weighed against exposed wood chips in the other to determine water absorption from the atmosphere? Just a thought.
If this lot proves to be rubbish at least I have enjoyed the research and maybe stirred a few thoughts.

Don Cleavin

The top item, the Ringrose CO2 indicator was commonly fitted in all diesel ‘S’ and ‘T’ boats that I was in. Though hardly ever used.

Leave a Reply