Hi John,

Well, it's not exactly going to sell a lot of seismometers, but it does 
give credit where credit is due. It will probably be shortened to EDP 
Seismometer, but what the heck. It's certainly OK with me, and since I 
haven't heard from anyone at UWA recently, let's go with it.

So "Ewing Duplex Pendulum Seismometer" it is, unless someone chimes in with 
a major dissenting opinion.

Dave...

PS 80 degrees here in North Carolina today> Spring has sprung!

At 10:44 PM 3/31/03 -0700, you wrote:
>Hi Dave,
>
>Thanks for finding this information!  What do you think we should call this
>type of system?  How about "Ewing duplex-pendulum seismometer?"
>
>Cheers,
>John
>
>At 03:20 PM 3/31/2003, you wrote:
>>All,
>>
>>I have finally hit pay dirt in my quest for the original folded pendulum 
>>seismometer.
>>
>>The original instrument of this type was built in 1882 by Dr James Ewing. 
>>I believe that Dr Ewing was in Tokyo at the time. His instrument used a 
>>common pendulum coupled to an inverted pendulum so as to decrease the 
>>stability of the common pendulum. It appears to me that this was a 
>>two-axis instrument. Dr Ewing referred to it as a "Duplex pendulum" 
>>seismometer.
>>
>>History has it that a number, possibly ten of these instruments were 
>>placed at sites in Northern California and Nevada during 1887-1888. 
>>Seismographic observatories at Berkeley and Mount Hamilton had duplex 
>>pendulum seismometers.
>>
>>Perhaps an avid researcher in California might be able to actually find 
>>one of these instruments.
>>
>>Dr Ewing built many different seismometers and, along with Dr Thomas 
>>Gray, He seems to have been one of the founders of modern seismological 
>>instrumentation.
>>
>>The single axis instrument which I constructed is certainly not identical 
>>to the two-axis unit of Ewing, but it employs the same principals and is, 
>>in many ways similar to his duplex pendulum design.
>>
>>My best to all,
>>Dave...
>>
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