I haven't taken them apart, although given
their weight to size ratio, I wouldn't be
surprised that there is mercury inside.



Steve Hammond wrote:
> 
> David, that a find. Is there any signs of mercury inside it as described
> in the text? The pipe is definitly a rubber tube connector.
> 
> Regards, Steve Hammond
> PSN San Jose, California
> 
> David & Betti Chase wrote:
> >
> > 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
> snip snip
> >  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?
> > >
> snip snip
> 
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