Lowell. — Geological Facts. 3AS 



feet in its cross diameter, and there were several from ten to fifteen, 

 twenty and twenty five feet. 



2. Some of the intruding masses do not go through to the upper 

 surface ; they are hterally wedge shaped, having separated the lay- 

 ers of mica slate below, and then in their ascent dying away be- 

 tween them, and terminating in a point or an edge, the mica slate 

 closing in, resuming its continuity, and continuing upward unbroken. 



3. The reverse of this arrangement is observed in a few cases, 

 the broad part of the wedge-shaped mass being upwards, sometimes 

 at the surface, and dying away downward. Tn this case, the melted 

 trap probably overflowed fi'om a concealed vent or was driven later- 

 ally in, and thus filled fissures in the mica slate, which were formed 

 by the heaving from below, and were left gaping upward and ready 

 to receive the molten flood. 



4. The contortions of the mica slate, produced by the fiery inva- 

 der are very numerous and striking ; they are such as we might sup- 

 pose would arise from a mighty force exerted from below, elevating, 

 severing, bending and tearing the stratified rocks among whose 

 peaceful beds, the melted trap was rudely injected. 



This confijsion, every where remarkable, is particularly conspicu- 

 ous in the deepest part of the cut, where, on both sides, the mica 

 slate is in vast disorder, and the intmsive trap is interlocked among 

 the lacerated strata, holding them fast as with an expirmg grasp. 



5. The injected trap is seen on both sides of the cut, towering to 

 the topmost cliffs, on the right and left, and continuing unbroken 

 across the bottom of the cavity. The strata of mica slate also ac- 

 company the trap on both sides, 



6. There are, at the junctions of the two rocks, indisputable 

 marks of igneous action ; in many places the mica slate is much in- 

 durated by the heat, and there is an undefinable blending of the two 

 rocks, portions of both being united by mixture as well as by partial 

 and hasty fi.ision or thoroughly assimilated by a full melting. 



7. There are numerous dissevered masses of mica slate, ofi:en of 

 considerable magnitude, which have evidently been torn off" by the 

 violence and heat of the injected trap, and borne along in the melted 

 mass ; there^are also detached portions of trap mixed with the mica 

 slate, and whose connexion with the main currents cannot be, in ev- 

 ery instance, traced in the actual section of the ledges, but which 

 without doubt, exists threaded and contorted in devious fissures, in 

 the interior of the broken rocks. 



