Hello,

I originally posted the query about the geo
phones.

If you have an interest , there is a oicture
at the following address:

http://www.mint.net/~chase/geophone.jpg

David Chase

Steve Hammond wrote:
> 
> Greg, the Chinese "instrument" is the Seismoscope built by Chinese
> scholar Chang-Heng about 132A.D. I found the discription of the Geophone
> even more interesting. It reminded me of a pre WWI deveive I read about.
> Here is the text description.
> 
> Source: A.S. EVE and D.A. Keys, 1938, Applied Geophysics, Cambridge at
> the University Press Page 230
> 
> Seismic Methods  "Thus geophones were used in the War, and may be used
> in mines for detecting the direction of such disturbances as blasting or
> the noise of a pick in tunnelling. Two geophones are employed of similar
> size and construction, in each of which an iron cylinder floats on
> mercury, while above the iron is a layer of enclosed air connected
> through a small hole with a rubber tube leading to the observer's ear.
> One geophone is thus connected to the right ear, the other to the left.
> The shock comming through the ground displaces the case of the geophone,
> while the inertia of the mercury and iron tends to hold them relatively
> at rest. Hence, the air is driven in rhythmic puffs through the holes
> and tubes to the observer's ears, and he hears the sound in a quite
> natural fashion. The remarkable physiological phenomenon of "binaural
> hearing" now comes into play."
> 
> What has got my attention is that you did not describe any electrical
> connections and you mentioned an iron section. Is there a coil in the
> Pollard Geophone? Or could it be a orignial pre WWI geophone?
> 
> Regards,
> 
> 
> Greg wrote:
> >
> > I got another email from my Geophone FAQ. Again, I can't really answer
> > the question. I'd appreciate any thoughts for the reply and the FAQ. I
> > asked the author to join the list, but I don't think that happened yet?
> >
> > 
> > I have a pair made of brass top and bottom
> > plates seperated by what looks like an iron
> > section. Ther are about 3 1/2" in diameter
> > and 1 3/16" thick ( each section being 3/8").
> >
> > They are marked "GEOPHONE Joseph G Pollard
> > Co. New Hyde Park, N.Y. 1863".
> >
> > My questions are :
> >
> > 1. Could they really be that old?
> >
> > 2. If they are, what were their uses during
> > that period ?
> > 
> >
> > I've seen the antique Chinese "instrument" with the balls that fall out
> > of the dragon mouths, but how far back does something like this go? I
> > know that there have been some large earthquakes "recorded" throughout
> > history, but I thought that most of the really old ones are estimated by
> > damages and people's guesses.
> >
> > The list has been a little quiet lately hasn't it?
> >
> > As always, thanks for responses,
> > Greg
> >
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