186 Analj/sis of Scientific Books. 



granite. At a certain distance from the origin of the vein, the 

 granite ceases to contain mica ; further on, the feldspar disap- 

 pears ; and the vein thereafter terminates by a simple thread of 

 compact quartz. All the veins terminate in a sharp point. Near 

 the top of the mountain, the most considerable veins are ob- 

 served ; of which two parallel ones are from three to four feet 

 in length, and one foot wide at their origin. Others are more 

 extended, but narrower ; and some are scarcely an inch thick. 

 In general, the straighter the vein the more finely granulated 

 is the granite. The granite of the veins and that of the moun- 

 tain, form one continuous body ; they are separated by no 

 interval, not even by the slightest fissure. The grain and the 

 nature of the veins, at the places where they enter the schist are 

 so perfectly similar to those of the general mass, that it is 

 impossible on viewing the granite, to say where the mass ter- 

 minates, and the vein begins. Hence it may be safely asserted, 

 that the epoch of the formation of the mass of granite is con- 

 temporaneous with that of the vein. But a difficulty occurs 

 when we try to determine the relative antiquity of the granite 

 and the schist ; for, in such a predicament, the system of 

 superposition of Werner, is in manifest contradiction with his 

 own theory of veins. 



According to the system of superposition, every rock whose 

 beds rest on another rock, is of a more recent origin than the 

 rock on which it reposes. We ought therefore to conclude, 

 that the clay-slate is more modern than the granite. But, on 

 the other hand, the theory of veins teaches us, that the sub- 

 stance of the vein is more modern than the rock which includes 

 it, since the rent must of necessity have preceded the matter 

 which fills it up. Thus, the granite of the veins should be 

 more recent than the slate which contains it. Yet, the granite 

 of the veins and that of the rest of the great granitic mass are 

 obviously identical and contemporaneous ; hence, the slate 

 ought to be more ancient than the mass of granitic, on which 

 it lies. These two propositions are evidently contradictory and 

 incompatible. Which of the two is the more probable ? Mr. 

 Necker does not hesitate to affirm, however extraordinary it 

 may seem, according to the ideas current among geologists, 

 that the latter is the more probable opinion ; and, that conse- 

 quently the granite of the island of Arran must be regarded as 

 newer than the schist which envelopes if. In fact, we may in 

 certain cases conceive how a mass may cover up another 

 without the upper mass being the more modern of the two. 

 But we cannot imagine how the substance of a vein can have 

 pre-existed the rock which encloses it ; how a figure cast in a 

 mould, can have existed before that mould was formed. Two 

 other circumstances in the granite veins of Tor-nid-neon serve 

 to confirm this conclusion. 1st. We see clearly that the crys- 



