INTRODUCTION. IJ 



to refer to instrumental records. When the vibrations of 

 the ground have only been along the line joining the 

 observer and the epicentrum, the disturbance might be 

 called ' euthutropic' A disturbance in which the promi- 

 nent movements are transverse to the above direction 

 might be called ' diagonic' If motions in both of these 

 directions occur in the records, the shock might be said 

 to be ' diastrophic' • If there be much vertical movement, 

 the shock might be said to be ' anaseismic' Some disturb- 

 ances could onlj be described by using two or three of 

 these terms. 



