Hi Paul,

There was an instrument called a seismoscope that was an inverted 
pendulum that scratched a smoked glass plate to record the 
2-dimensional motion of the pendulum.

If swung in the absence of ground motion, a record like that of a 
Harmonograph would be generated.

See:  http://www.data.scec.org/Module/sec3pg07.html
and


There is a picture of the outside of a seismoscope posted here:
http://www.geocities.com/meredithlamb/page022.html

I can't find one right now that shows the inside.  Does anyone have 
such a picture?

With out any indication of time, these records were very hard to interpret.

Cheers,
John

At 01:06 PM 6/29/2007, you wrote:
>Folks,
>
>With all the talk about pendulums, it reminded me of a article I saw 
>in a magazine once.
>
>The article was about a Harmonograph.
>
>I won't even think about the math involved that would be Chris's department.
>
>It seems to me like a mechanical pendulum adding machine.
>Where the length, decay, friction.. all play a roll in drawing not a 
>seismogram, but a ...?
>
>Early predecessor to the Spirograph toy??  Interesting, and not too 
>far off topic.
>
>PauLC
>W1VLF
>
>http://physics.kenyon.edu/EarlyApparatus/Oscillations_and_Waves/Harmonographs/Harmonographs.html
>
>


__________________________________________________________

Public Seismic Network Mailing List (PSN-L)