258 



BOARD OF AGRICULTURE. 



haps very much in the same way that we thought a connection 

 existed between the limestones exposed at Holmes' and Ingraham's 

 quarries. 



Trap Dikes. In the principal quarries of limestone in Rockland 

 and Thomaston interesting dikes of trap occur. To the workmen 

 they are a nuisance, but to the geologist are full of interest, as 

 indications of ancient molten masses like lava, in this vicinity. 

 AVhen the rocks about here were being tilted up at ^rarious angles, 

 folds were formed and many large masses were broken apart. 

 Molten matter from beneath then crowded up and filled many of the 

 crevices. When this lava had cooled, probably quite slowly, these 

 dikes were found to be the result. These dikes we have seen in 

 the Beechwoods, several of the Meadows, near Rockport, and in 

 the Blackington Corners quarries. They are seen now as walls 

 upon the sides, in the middle or crossing the quarries, being com- 

 posed of a dark, tough, very fine grained rock. Occasionally a 

 row of trap nodules seerps to. take the place of a dike. 



Fig. 42. 



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Trap Dike in ike Beechwoods Quarry. 



An interesting example of a trap dike at the Beechwoods quarry 

 is represented in Fig. 42. It is in the sketch seen to form a wall, 

 which curves, and at the right hand side passes round a pillar of 

 limestone facing the observer. It then crosses to the other side 

 of the quarry, and continues on in a course parallel to its first ap- 

 pearance. That part seen in the sketch resting against the frame- 

 work of limestone, is composed of numerous small columns, piled 

 up with great regularity, as if done by hand, just as many sticks 

 of wood are laid up with the sawed ends in front. At another 

 quarry the limestone has been excavated from both sides of the 



