452 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



NORMAi, CONTACTS OF DIABASE ON SANDSTONE. 



East of the Bay road, the most easterly road crossing the Holyoke 

 range, no direct contacts are visible. Pieces of the sandstone indurated by 

 the trap have been found in the neighborhood of the lower contact. 



At the northwest shoulder of Rattlesnake Knob — the conical hill east 

 of Norwottuck, or Hilliards Knob — a very interesting contact is exposed. 

 If one goes east from the fault which limits the trap at the east foot of the 

 peak, and follows the contact as nearly as may be across the talus at the 

 north foot of the peak to a point below and a few rods west of where the 

 peak sinks down to the ridge which connects it with Norwottuck, one finds 

 a vertical wall of the trap projecting over the sandstone where the contact 

 is exposed. The diabase is fine-grained, and the dai'k-red sandstone is 

 baked for 3 feet down to an unusual degree into a rock closely resembling 

 a schalstein. 



At the northwest corner of the sharp peak of Norwottuck, at the corner 

 of a cleared field, a contact can be observed. The sandstone is indurated 

 for a short distance. 



The next point is more accessible, being to the west of and just over 

 the Notch road at the north corner of the "Devils Garden," where the trap 

 can be seen from the road below to be overhanging. Here the sandstone 

 is coarse and is darkened and indurated to a complete quartzite for a foot 

 down, and slightly vesicular. 



There is another exposure on the south side of the north footpath to 

 Mount Holyoke.^ 



The next place is just north of Titans Piazza, a place figured by 

 President Hitchcock,^ and here the diabase is at its base very black and 

 compact and full of vertical steam holes a foot or more long. The sand- 

 stone below is baked into a tough quartzite or hornfels for a foot down. 



CONTACTS OF UNDER-EOLLED DIABASE CONTAINING INCLUSIONS OF LIMESTONE. 



A remarkable wall of trap is exposed at low water of the river at the 

 north foot of Titans Pier, just where the Hadley town line reaches the 

 river, below a small cemetery. The contact is visible for 100 feet. The 



' E. Hitchcock, Am. Jour. Sci., Ist series. Vol. XIII, 1828, p. 218. 

 ' Final Report, Geol. Mass., 1841, p. 640. 



