256 STRATIGRAPHICAL GEOLOGY. 



Willard, and Crawford ; and the veins do not extend far away from the 

 ragged edge. 5. The relations of the Labrador system to the Montalban 

 are of much importance in this connection. Fig. 20, PI. VIII, shows the 

 Montalban elevated at angles of sixty degrees, overlaid by labradorite 

 rocks dipping ten or twelve degrees upon the average. Similar sections 

 could be drawn for the Waterville area, save that the lower formation is 

 older than Montalban. These sections appear to indicate that the first 

 elevation was very extensive, and that it was mainly effected before the 

 deposition of the Labrador system. Granting that the Labrador system 

 is well established as a geological horizon, it follows that the whole At- 

 lantic system precedes it in time, and is to be regarded as a subdivision 

 of the Laurentian group rather than of anything later. 



These considerations lend probability to the suggestion, that not long 

 after the close of the Montalban period there were disturbances resulting 

 in the ejection of melted rock, and the beginning of the elevation of the 

 Mt. Washington range. At this epoch it is probable that the principal 

 part of the elevation was effected, the range having attained a great alti- 

 tude. It is likely that there has never been a more important epoch of 

 elevation in the physical history of New England. 



The next period of elevation, of which evidence is afforded by the 

 structure of the range, occurred after the deposition of the andalusite 

 schists. It may be premised that there were ridges upon both sides of 

 the later schists, so as to constitute the hydrographic basin in which they 

 were deposited. Two epochs of this elevation can be insisted upon, the 

 first to bring the secondary series into the same position with the pri- 

 mary; and, lastly, an interesting upheaval that seems to have determined 

 the great altitude of Washington. On page 1 1 8 it is stated that the sec- 

 ond fold has its axis almost at right angles with the first. The axes of 

 the smaller curves along the road near the third mile-post run N. 30° W. 

 Others higher up, that are more constant, dip N. 2,^° E., twenty-seven 

 degrees more southerly than those first mentioned. It is not common, 

 or at least it has not been often stated in geological treatises, that the 

 same ledge will show evidence of forces acting nearly at right angles to 

 each other in successive periods. It is the minor curves that run N. 30° 

 W. The result of this reduplication has been the intensification of the 

 altitude, just as a change of wind produces higher waves in the ocean. 



