4 Sir G. S, Mackenzie 091 the most recent 



of trap has been the most recent instance of matter having 

 been protruded from below into fissures above. Many inva- 

 sions are indicated by the display of numerous varieties of 

 granite, and of one granite cutting another ; and the same is 

 the case with trap and other invading matter. The most re- 

 cent of all these appears to have been that which filled the 

 rents of the secondary strata and beds of trap with trap ; and 

 this must have happened before the crust of the earth was so 

 displaced as to bring its broken parts into their existing state. 

 All the matter in veins must have been solid before being ex- 

 posed to view. It is not improbable that the invasion of pro- 

 truded matter to a certain extent disturbed the rocks into 

 which it passed ; but it does not appear that this had elevat- 

 ed the land to any considerable degree. It would rather ap- 

 pear that, before the rupture was eff'ected which gave to the 

 surface its present shape, it w^as very little elevated. Hence 

 the general warmth of the climate in the temperate zone, in 

 so far as influenced by the sun, must have been greater than 

 it is now ; and there seems to be nothing in the way of the 

 supposition that the temperature of the crust of the earth was 

 also greater from the influence of internal heat. These 

 causes combined may have rendered the temperate zone 

 warmer by many degrees than it is now ; and it may have 

 been habitable by those animals and plants, the remains of 

 which, in certain localities, have caused much difliculty in 

 geological speculation. 



With respect to the heat from the internal source, if we re- 

 flect a moment, it will appear probable that it was formerly 

 greater in amount, from a consideration of the phenomena 

 which the most recent cataclysm has brought into view. The 

 rents which we now see filled with protruded matter could 

 not have been made by a force sufficient to elevate the rocks 

 in which they were made very much out of their original po- 

 sition, because in that case the rents would not probably 

 have been filled. It was necessary that the strata should still 

 rest on the melted matter when they were broken, in order 

 that the pressure (operating, perhaps, in some other locality) 

 might force it into the openings, and continue until it became 

 solid, preventing a collapse of the sides of the fissures* This 



