Seismological Investigations. 



103 



center of gravity this hole is suddenly diminished in diameter 

 by a small amount, affording a shoulder against which rests a 

 cross piece filling symmetrically only a part of the opening and 

 carrying at its center, which is on the axis of the cylinder, a 

 fine steel point. This point rests in a small depression on the 

 inner side of a link, to which is attached a long steel needle as 



shown in the cut. The upper end of the link hangs upon a 

 hook made of wire of the same diameter and rigidly attached 

 to the supporting frame of the instrument which is of iron. 

 By this arrangement for the suspension of the heavy mass, the 

 link with its needle projecting downwards, has considerable 

 freedom of motion in all azimuths, with little frictional resist- 



