56 AN OUTLINE OF THE 



another. These dikes are commonly from two to ten feet 

 wide, standing nearly vertical, trending somewhat east of 

 north with rather direct courses. They are found on low- 

 land and highland, from water's edge to mountain top. 

 They nowhere exhibit the smallest indication of overflow ; 

 even over the summit of Green Mountain they are as dense 

 and as well contained within their walls as at sea level. 

 Hence, when they were intruded, the rocky mass must 

 have risen above the mountain tops of to-day. It is pos- 

 sible that their lavas may have reached the surface of 

 their time, and maj"- have there overflowed, much in the 

 same way as the felsites ovei'flowed on a lower surface 

 long before ; but we have no evidence of such surface 

 action. The dikes, as now revealed, are deep structures, 

 and with the diorites and granites proclaim the greater 

 mass that the rocks once possessed, and the wasting that 

 the region has since then suffered. 



The Great Denudation. 



If the greenish schists are older than the bedded rocks, 

 as may be supposed, it is eminently possible that the 

 unrecorded time between the deposition of the two series 

 witnessed a denudation as great as that which we have 

 now to consider ; but our attention cannot be well directed 

 to that long lost chapter of the Island's history. The 

 chapter is at present only a matter of fair inference, and 

 it never can be fully reconstructed. It is like those many 

 lapsed periods of ancient human history, unmarked by 

 recoi'ds of great battles or by the dethronement of kings, 

 over which our imagination passes so lightly, and with so 

 little appreciation of all that they contained. But with 

 the later denudation, by which the present form of the 

 Island has been fashioned, we have much to do. It calls 

 for study as attentive as that by which the making of the 

 rocks is discovered. A full understanding of the geological 



