lO SIEUR DE MONTS NATIONAL MONUMENT. 



and the penetration of the regional rocks themselves by narrowing gra- 

 nitic arms or dikes, clearly show that the granite is the later comer, and 

 that it came molten, breaking its way with tremendous power into the 

 ancient rocky crust under some vast, compelling pressure; at last, when 

 the impelling forces were satisfied, it came to a halt and slowly froze into 

 a rigid mass, holding in its grasp innumerable fragments gathered from 

 the rent and fractured walls, whose cracks it fills. 



This granitic outburst is the greatest event in the geologic history of 

 Mount Desert. It was of colossal magnitude. The energy of its intru- 

 sion can not be conceived. Not that the intrusion was suddenly accom- 

 plished, for no conjecture can be made as to the time it took, but that it 

 was effected against enormous resistances and involved the movement 

 of gigantic masses. 



The granite mass disclosed in these ancient monuments of the geologic 

 past is at least a dozen miles in length and four or five in breadth at 

 widest, with roots far wider spread beneath the level of the present sur- 

 face. No one can give a measure of the greater height to which it once 

 ascended, and he would be a daring geologist who would set a limit to 

 the unsounded depths from which it rose. The uprising may have re- 

 quired many historic ages; it may have been relatively rapid; but that 

 it was progressive, not instantaneous, is clearly to be seen upon examina- 

 tion of the granite margins. 



The bare ledges and cliffs of the southeastern coast especially afford 

 wonderfully clear illustrations of the molten stone's intrusive processes. 

 Here we may follow the upward-driven granite forcing its way into 

 narrowing cracks among the older rocks; there great fragments of the 

 older rocks have been caught up in it and partly melted by its heat per- 

 haps. Sometimes a block of the ancient regional stone may be seen 

 divided by granite-filled fissures whose fractured walls can still be matched 

 with certainty, striking instances of which are shown on the eastern side 

 in the narrows of the Somes Sound fiord. The now rigid granite then 

 yielded so perfectly under the heat and tremendous pressures acting on 

 it as to penetrate the narrowest cracks and crevices, following them down 

 to hairlike fineness. Nowhere in the world, indeed, may the geologist 

 or traveler find better or more impressive illustration of the manifold 

 processes of deep-seated intrusion than on the wave-swept ledges of the 

 island's southern coast between Somes Sound and Frenchmans Bav. 



