So EFFECTS OF UPHEAVAL. 



announced, viz., that these disturbances were probably connected with 

 the effects of internal heat. 



We shall assume, then, that granitic, and basaltic or trappean 

 rocks, and others exhibiting the same phenomena, were crystallised 

 from a state of igneous fusion, and were, sometimes in a fluid, and 

 sometimes in a solid state, impelled upwards towards the surface of the 

 earth, as analogous substances are now ejected or poured forth as fluids 

 through volcanoes, or lifted in a solid state by earthquakes, &c. 



In proportion as we approach the mountains where the greatest 

 violence has been exerted to break up the strata, raise the granite, 

 and inject the basaltic dykes, we find the dislocations increased in 

 number and importance, and the confusion of the stratification more 

 prevalent. 



The central nucleus or axis of many mountain districts is a 



mass, or a series of masses, of 

 granite and other unstratified or 

 metamorphic rocks, from which 

 on all sides the strata are 

 found dipping away at high 

 an gl es - In such cases there 

 can be seldom room to doubt 

 Fig. 34 . i and 2 . Primary strata. that the elevation of the moun- 



3. becondary Strata. , . , . , , . , , 



tain ranges and the disturbance 



of the strata was occasioned by the same violence which uplifted 

 the granite. 



The area of granite disclosed between the opposite slopes of 

 strata is indefinite, sometimes very large, sometimes very small, 

 sometimes it is entirely covered over by the rocks which it has 

 uplifted, but not protruded through or perforated. The general analogy 

 in the composition of mountains, in the strata which surround them, 

 and in the dislocations which abound in their vicinity, prove that 

 one common subterranean force has produced all the phenomena in 

 question. 



Basaltic rocks frequently, perhaps generally, show themselves in 

 situations removed from the granitic regions, on the flanks of moun- 

 tains and often in lower ground. In numerous instances, basalt fills 

 up the fissures between the elevated and depressed portions of dis- 

 located strata, and as it cannot be doubted that such a fissure would 

 soon have been filled up by other substances, it is clear that the 

 melted basalt was injected nearly at the same time as the dislocation 

 was produced; that is, that both were local effects of diminished 

 pressure acting on regions affected by internal heat. How this 

 heat was produced, is a question that will receive consideration 

 subsequently. 



Analogy of Mineral Veins and Trap Dykes. So great a general 

 analogy prevails between some mineral veins and basaltic dykes, that 

 in almost all hypotheses their origin has been assumed to be similar 

 in kind. Both in the same manner divide the strata ; in both the 

 materials are crystalline, often such as are not known to be pro- 



