Interior of the Globe. 43 



ance are comparatively near (as Comrie and Oban), their ac- 

 tion may be independent of each other. The agitation felt 

 over so wide a region at the great earthquake which destroyed 

 Lisbon, and on other occasions, may be considered as a mere 

 vibration propagated through the outer part of the crust, 

 from the focus of disturbance, like the tremor which accom- 

 panies the blasting of rocks. From the independence of ac- 

 tion, he reasonably infers that the seat of disturbance cannot 

 be at any great depth. These views harmonise with the con- 

 clusions of Mr Hopkins, deduced from very diflPerent data. 

 While, therefore, some of the basins of fused matter may be 

 of great extent, like that under the Andes (supposing the 

 synchronism of volcanic action over the long line to be estab- 

 lished), others may be very small ; and the simultaneousness 

 of disturbance at distant spots may be merely the effect of 

 vibrations propagated from the centre. 



I shall advert in the briefest terms to some hypothetical 

 views thrown out by Mr Hopkins, as to the changes of form 

 the globe has undergone. If the earth was originally fluid, it 

 might pass to the solid state in two modes. The heat would 

 be continually dissipated from the surface, and would there- 

 fore be greatest at the centre ; and so long as the mass was 

 fluid, the inequality of the heat would cause a constant circu- 

 lation betwixt the surface and the centre. Now, if the efl*ect 

 of heat in preventing solidification was greater than the effect 

 of pressure in promoting it, solidification would begin at the 

 surface, where a crust would be formed, and would constantly 

 increase in thickness, by layer after layer added to its under 

 side. But if the eff'ect of pressure in promoting solidification 

 was greater than the eff'ect of heat in preventing it, solidifica- 

 tion would begin at the centre and extend outwardly. While 

 the process was going on, circulation would continue in the 

 fluid part exterior to the solid nucleus. But before the last 

 portions become solid, a state of imperfect fluidity would 

 arise, just sufficient to prevent circulation. The cooled par- 

 ticles at the surface being then no longer able to descend, a 

 crust would be formed, from which the process of solidification 

 would proceed far more rapidly downwards than upwards 

 from the solid nucleus. Our globe would thus arrive at a 



