48 AN OUTLINE OF THE 



finer texture near their boundaries, where they are chilled 

 and solidified quickly ; while larger crystals and coarser 

 texture are produced within the mass, where the cooling 

 is more gradual. Even a broken bar of pig iron illus- 

 trates a variation from fine to coarse texture in passing 

 from its surface to its interior. 



The fine texture of the margin of the granite, the inclu- 

 sion of numerous angular fragments of the country rocks 

 along the borders of the granite belt, and the penetration 

 of the country rocks by narrowing granitic arms, or dikes, 

 demonstrate that the granite is a later comer than the 

 other rocks, and that it moved from some former position 

 to its present position while molten, breaking its way into 

 the solid, rocky crust in its escape from some excessive 

 pressures that forced it to move ; until at last, when the 

 impelling pressures were satisfied, it came to a halt, and 

 slowly froze into a rigid mass, holding close in its grasp 

 thousands of fragments gathered from the enclosing walls. 

 The only imaginable source of supply for such a mass of 

 molten rock is in the earth's interior; and although no one 

 can well account for the forces by which the granite was 

 squeezed outward from its former position, no one can 

 justly doubt the reality of its out-thrust. The granitic belt 

 is indeed nothing more than a great irregular ragged dike, 

 pushed upward through the ancient rocky crust of the 

 earth. Many such intrusive masses are known elsewhere 

 in New England, and in other parts of the world. The 

 Blue Hills near Boston are largely composed of intrusive 

 rocks, amid surroundings much like those of the Mount 

 Desert range ; the rocky dome of Cape Ann is of similar 

 nature. 



The granitic outburst is the greatest event in the history 

 of Mount Desert. It is of colossal magnitude. The energy 

 of its intrusion cannot be conceived. Not that the intru- 

 sion was suddenly accomplished, but that it was effected 



