4J8 Mr Johnston ofi tlte Elevation of 



poles and dilating it around the equator, where the resistance of 

 the crust to the pressure from within would be least. This 

 process continuing, a time would at length arrive, when the 

 polar regions would no longer throw off any sensible quantity of 

 heat ; when their temperature would be constant, the caloric de- 

 rived from the sun in summer being nearly equal to that lost 

 by radiation in the winter, and when all sensible contraction 

 coHsequently would cease. But it is obvious that such a term 

 would arrive long before the equatorial parts of the earth had 

 reached their maximum of cooling, — while they were still con- 

 tinuing to give off heat and to contract. The whole compress- 

 ing force consequent upon contraction, would now be exerted in 

 the equatorial regions, and the earth in this state may be repre- 

 sented by a globe encircled by a broad belt, compressing it at 

 right angles to the axis. The effect of such a compressing force 

 on the inner mass must be to displace it, and to produce a ten- 

 dency to dilate in directions where the resistance is least. Now, 

 the compressing force, under the circumstances stated, being in- 

 sensible at the poles, all other things being equal, the eruption 

 or displacement, whether violent and of short duration, or gra- 

 dual and of long continuance, is most likely to take place in 

 high northern latitudes. But there might occur in lower lati- 

 tudes, weak points in the crust of the globe, which would be the 

 first to yield ; and wherever the point of minimum resistance 

 occurred, there the convulsion would naturally take place. 

 Where a point of small resistance occurred, an isolated moun- 

 tain would be thrown up ; a line would give direction to a moun- 

 tain-chain ; and, where neither occurred, it is easy to conceive 

 that a large tract of country might be elevated either at once, if 

 the resistance were at once overcome, or gradually, — the resistance 

 of the crust and the compressing force at the equator, remaining 

 uniform and nearly balanced. 



If, therefore, we admit the theory of the gradual cooling of 

 the globe, we recognise the existence, at every point on its sur* 

 face, of a compressing force which, at the equator, is now a 

 maximum, and in the elevation of the northern part of Scandi- 

 navia, an effort of the internal mass to liberate itself from that 

 pressure, by displacing the crust of the earth at a point of mi- 

 {umuin resistance. 



