In a message dated 7/13/01 2:50:44 AM GMT Daylight Time, ACole65464@....... writes: << I just scanned a small photograph out of an old catalog tilted "Geophysics & Geomagnetism", published by the Science Museum. The photo matches closely the instrument that you described in words. I picked a the copy of the catalog when I was visiting London 10-12 years ago. Go to the following Web page to see the scanned image (370K jpeg): http://hometown.aol.com/acole65464/SEISMOPICS.html >> Thanks Allan, Your very nice scanned image shows that it is a Lehman-type horizontal seismometer. The boom apparently extends back to a pivot point out of the picture with the mass supported by the turnbucle/cable going up at an angle. With the obviously very heavy mass stacked right up to the boom it would act like a Lehman seismometer. the photo shows two pins to restrain horizontal movement of the boom which extends into the complicated mechanism Ted describes. The mechanism looks like a system of compound levers that are a mechanical amplifier. I would guess that the nearest pen is amplified the least and records strong movement. What looks like two additional lever systems for the farthest pen probably amplify its movement additionally to show more detail in the seismogram. The pens and lever systems would provide drag that amounts to damping. Presumably the loop of paper runs for 24 hours so time could be measured from the start where the time of start would be marked on the paper loop. It is certainly an interesting mechanical device that could record earthquakes. Its sensitivity would depend on the lever system. The photograph shows what seems to be a carefully built and well designed system of levers that provide mechanical amplification. I hope Chris Chapman, who is an engineer, will figure out the amplification factor when he visits the museum in a couple of months. Best regards, Cap __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>