6 Sir G. S. Mackenzie on the most recent 



have been, we are yet ignorant, and probably will long con- 

 tinue ignorant of those terrestrial conditions which appear to 

 influence electrical eff'ects, in alternately warming and refri- 

 gerating the atmosphere. I make these remarks for the pur- 

 pose of shewing it to be possible, that the temperate zone 

 may have been warmer before the most recent cataclysm, 

 which may have effected so great a change in the electro- 

 magnetic condition of the earth as to create alterations in 

 atmospheric conditions sufficient to counteract, to a consider- 

 able extent, the influence of internal heat and of the sun. 



2. It is evident that, before the disruption of the crust 

 took place, there had been a vast exertion of expansive force. 

 This increase of force had probably been caused by additions 

 to the amount of vaporable matter collected and confined be- 

 twixt the crust and the greatly heated interior. When we 

 regard the enormous masses of matter that have been thrown 

 up from under the crust of the earth, as indicated by the vast 

 amount of granite and other protruded matter which we 

 find among the strata ; and when we contemplate, not only 

 the amount of trap in veins, but the very great extent of trap- 

 beds heaped on one another, and forming lofty mountains, as 

 seen in almost every quarter of the globe, and which are now 

 generally admitted to have been sub-marine lavas, we cannot 

 refuse assent to the proposition, that when all these masses 

 were thrown up, immense cavities were left between the solid 

 crust and the igneous matter below. Such cavities would not 

 be vacuous, but filled with vaporable matter, probably red hot 

 water, and exerting an enormous expansive force. That this 

 was the condition of things appears the more probable, as 

 nothing has been noticed, at least so far as I know, shewing 

 that when the crust of the earth was broken up any stony 

 matter had been erupted among and over the strata. Had 

 there been no elastic matter interposed between the crust and 

 the liquid matter below, we might have been at a loss for ex- 

 pansive force. Had there been any other power pressing the 

 liquid matter upwards against the crust, that matter would 

 have been forced up like lava, and have filled hollows, where 

 we should have found it. I therefore assume, as the ground- 

 work of my hypothesis, that there existed, between the crust 



