EARTH PULSATIONS. 337 



surface must be taking place, causing variations in 

 inclination of one portion of the earth's crust relatively 

 to another. 



Although it is possible that phenomena like the 

 surging of levels may be attributable to causes like these, 

 we can hardly attribute the other phenomena to such 

 agencies. 



Rather than seek an explanation from agencies 

 exogenous to our earth, we might perhaps with advantage 

 appeal to the endogenous phenomena of our planet. 

 When the barometer falls, which we have shown corre- 

 sponds to an upward motion of the earth's crust, we know, 

 from the results of experiments, that microseismic motions 

 are particularly noticeable. 



As a pictorial illustration of what this really means, 

 we may imagine ourselves to be residing on the loosely 

 fitting lid of a large cauldron, the relief of the external 

 pressure over which increases the activity of its internal 

 ebullition — the jars attendant on which are gradually 

 propagated from their endogenous source to the exterior 

 of our planet. This travelling outwards would take 

 place much in the same way that the vibrations con- 

 sequent to the rattle and jar of a large factory slowly 

 spread themselves farther and farther from the point 

 where they were produced. 



Admitting an action of this description to take place, 

 it would then follow that this extra liberation of gaseous 

 material beneath the earth's crust would result in an 

 increased upward pressure from within, and a tendency 

 on the part of the earth's crust to elevation. If we 

 accept this as an explanation of the increased activity 

 of a tremor indicator, then such an instrument may be 

 regarded as a barometer, measuring by its motions the 

 variations in the internal pressure of our planet. 



