I am a bit confused regarding the construction of a Lehman (Garden Gate) 
seismo.
Text books at the local university library indicate Garden Gate seismographs 
with mass of 25 kg or more.  However, simular seismographs made by PSN 
members use masses of about 7 lbs.  Why the difference?  Is the larger mass 
more or less sensitive?
Additionally, in the text book examples reflecting the principle of the 
Garden Gate seismograph, they all show the boom slightly tilted down towards 
the mass end.  However, most instructions I have seen on the list I believe 
states that one should "level" the boom.  Which is best for sensitivity - and 
if the boom should be tilted to what degree is appropriate?
A number of pictures on PSN web sites show a long thin rod as part of the 
boom suspension.   Others just show a turn-buckle.  What purpose does the 
long thin rod serve?
Any clarification would be appreciated.
Jim Allen
Cerritos, Calif.

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