> Ian, I now know what you're *really* up to -- you are 
> trying to replicate
> the Michelson-Morley experiment!
>
> "Vibrations were further reduced by building the apparatus 
> on top of a huge
> block of marble, which was then floated in a pool of 
> mercury."
>
> http://en.wikipedia.org/wiki/Michelson-Morley_experiment


Nah. He's trying to build a memory - he did say it was for 
use with a PIC.

        http://en.wikipedia.org/wiki/Delay_line_memory

        http://ed-thelen.org/comp-hist/vs-univac-mercury-memory.html

        http://www.maxmon.com/delay1.htm

I have one in my 'museum' which uses a similar method but 
stores the data in a spiral of wire. Acoustic delay line 
memory.

If you can't get enough Mercury for a memory you could try a 
CRT memory.

    http://en.wikipedia.org/wiki/Williams_tube

Then you can read it optically personally at the same time 
the computer (PIC) is accessing it. AND see its memory usage 
patterns to boot.

And friends.
Including a picture of Grace Hopper. We won't mention the 
COBOL manual.

        http://infolab.stanford.edu/pub/voy/museum/pictures/display/2-1.htm#tube

Variant of acoustic delay line memory half way down. .



        Russell 

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