OF DENISON UNIVERSITY. 13 



rock is the common freestone used so extensively for foundation work 

 and building purposes. In Plate A can be seen the face of the solid 

 rock which is worked, and a considerable portion of the broken ma- 

 terial above it. Near the center of the illustration will be seen a large 

 block of the harder portion of the rock, which has its corner broken 

 by quite a number of curved fracture lines nearly parallel to each 

 other and making almost a perfect truncation of the corner. These 

 broken portions have slipped quite a little on the block in a downward 

 direction, as seen by the fine lamination lines, thus indicating that the 

 fracturing force was from above in a vertical line or but varying 

 slightly from the vertical, and that it was not lateral, else the motion 

 would have been in the other direction. Plate B represents a view of 

 the rocks above the quarried rock in the same exposure, but on a little 

 larger scale. Here it can be seen the rocks are fractured into all 

 kinds of forms, having all sorts of curved and irregular faces, and it 

 is impossible to trace any continuous jointing or stratification planes. 

 However, in the individual fragments it is evident that the planes of 

 stratification have been functional in determining form. On the top 

 of this hill was found a number of erratics, and on the south side of the 

 hill is a large deposit or glacial drift. 



The next quarry illustrated, is located about one and a half miles 

 south of Newark, and was chosen because it was about on an equal 

 elevation with the first, and the exposure can be identified as 

 being of exactly the same geological horizon, by a thin layer of 

 coarse grained sandstone which is present in both. If, however, we 

 study the rocks in this quarry, as will be seen in Plates C and D, 

 which are taken from different parts of the same exposure, we will find 

 that they are broken largely in but two directions, one along the 

 planes of' stratification, which can be followed through the whole 

 quarry, no matter how near we approach the surface, the other almost 

 at right angles to the first, vertical or nearly so, and corresponding 

 in direction to the joint planes of the underlying harder rock. It will 

 be seen also in Plate D especially, that no matter how close the rocks 

 may come to the surface at the side of the hill there is no apparent 

 breaking over in concoidal fractures. We also notice that the disinteg- 

 ration depends almost entirely upon the varying composition of the 

 individual strata. No erratics were found on top of this hill, al- 

 though they were quite abundant in the proximate valley, and drift 

 material is also abundant at the bases of the neighboring hills. Many 



