18 ART. ]. S. KÜSAKABE : FREQUENCY OF 



lead piece D, may be only slightly heated by virtue of the bad 

 conductivity of the lead piece B. 



The higli degree of heat conductivity in copper, i.< analogous 

 to the small hysteresis of old rocks'-"", while the lo\^ melting point 

 of lead corresponds to the inferior elasticity of new rocks. To 

 say that, copper being a good conductor, may be easih* heated 

 even when the source of heat is remote, is wholly diflerent from 

 saying that it may be often melted under the t^ame conditions. 

 Although lead melts very easily, it does not conduct heat very 

 well, so that even the portion comparativ^ely near to the source 

 of the heat may remain solid. But it is so only when the part 

 intermediate between it and the source is also lead. If the inter- 

 vening metal is copper, the case is reversed. 



All these complicated phenomena find their analogy in the' 

 case of seismic Avaves. Whether a region is frequently visited by 

 seismic waves or is not can never be determined by the data re- 

 lating to that region alone. A severe damage does not necessaî'ily 

 indicate that the epicentre of the earthquake lies near by. How- 

 ever great the destruction is, it is nothing more than the suj^erfcial 

 effect of the earthquake which is wholly controlled by surrounding 

 conditions. The 7nain factor which determines the degree of 

 disturbance is the geological distribiUion of the rocks in the 

 lühole domain. 



The existenee of the so-called sympathetic shock or Relais- 

 heben is also due to the reason just stated. In the above illustra- 

 tion,' one wdio knew nothing of the thermal properties of the 

 metals might call the melting of the lead piece ]) sympathetic. 



This iis simply :m anai.)gy, convent ioiialiy adopted lor sake of illustration. Tlie 

 Kciieral rnle tliat an analogy, however perfect, docs not explain all tla- facts connected with 

 it, Is true in this case. 



