PSN-L Email List Message

Subject: Re: Old equipment
From: Steve Hammond shammon1@.............
Date: Thu, 29 Jul 1999 02:30:11 -0700


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

_____________________________________________________________________

Public Seismic Network Mailing List (PSN-L)


[ Top ] [ Back ] [ Home Page ]

Larry Cochrane <cochrane@..............>