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