162 ON THE CHARACTERS AND DISPOSITION 



arguments shall here be stated in as brief a form as 

 possible; as there is little to be gained by dwelling 

 on illustrations of this nature. 



It is argued that heat does operate some of the 

 effects in question, and that it is capable of producing 

 them all, that no other agent is known equal to ful- 

 filling all the conditions, and that the effects are ana- 

 logous to those which are witnessed in the actions 

 of Volcanoes, whether as they relate to fusion, ex- 

 pansion, or elevation of the superincumbent strata. 

 It is next argued that the existence and permanence 

 of hot springs, and the antiquity, renewal, or existence 

 of Volcanoes, prove that the earth is the repository 

 of a deep seated and permanent source of heat. The 

 questions which regard the real nature of this heat, 

 whether it be permanent or but occasionally excited, 

 will be more usefully discussed when the nature of 

 Volcanoes is hereafter examined. 



Of Veins of Quartz and Carbonat of Lime. 



It remains yet to consider those rock veins which 

 belong neither to the families of trap nor granite. 

 The most abundant are those which consist of quartz 

 and of carbonat of lime, and they will be found more 

 analogous to mineral veins than to those which have 

 preceded. They even throw a sort of light on some 

 circumstances, at least, in the formation of those 

 veins ; although the greater part of that subject is 

 still involved in impenetrable obscurity. 



Veins of quartz are found in granite, gneiss, mica- 

 ceous schist, and indeed in every member of the pri- 

 mary rocks ; nor are they even excluded from the 

 secondary, although in these they are more rare. 

 They present many varieties of mineral character, 



