Hi Dave,     

       The details of the Lehman are given at   

       http://www.bgs.ac.uk/education/school_seismology/ 

       Click on seismometer for full details and a bigger photo.

       The bearings are crossed polished tungsten carbide rods. You can get 
periods of 30 seconds quite easily.

       Regards,

       Chris Chapman
   
Hi Dave=
,     



       The details of the Lehman are given at&=
nbsp;  



       http://www.bgs.ac.uk/education/school_s=
eismology/ 



       Click on seismometer for full details a=
nd a bigger photo.



       The bearings are crossed polished tungs=
ten carbide rods. You can get periods of 30 seconds quite easily.



       Regards,



       Chris Chapman