Plate 4. — Trap Ridge east of Greenfield. 



A winter view, looking east, of the trap ridge east of Greenfield. The sand- 

 stones project from the snow. The vertical walls above the snow consist of the 

 sand and glass breccia, which extends up to the base of the higher bluffs above. 

 Beneath the depression in the skyline north (to the left) of the tower is the quarry. 

 The path to the summit goes up the next depression to the north, and where the 

 snow lies deepest in this depression, nearly at the summit, is the place mentioned 

 on page 66, where the trap is so full of mud that it becomes a scoriaceous sand- 

 stone. Plates 5 and 6 are taken from the south face of the great boulder that lies 

 in the foreground. The trap sheet dips east from the observer, and the scoriaceous 

 upper surface of the sheet is not seen. 



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