PSN-L Email List Message

Subject: Re: A little Friday coolness
From: John Lahr johnjan@........
Date: Sat, 30 Jun 2007 12:02:23 -0700

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.


There is a picture of the outside of a seismoscope posted here:

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.


At 01:06 PM 6/29/2007, you wrote:
>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.


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