62 TRANSACTIONS OF THE [fEB. 1, 



sylvania, Poughkeepsie and Boston, and is eight miles south of the 

 New Yorlv State line. The dike is two miles from the small town 

 of Beemerville, which is the nearest place of any importance. It 

 is fourteen miles northwest of Franklin Furnace, where the famous 

 zinc mines are located. The general valley of the Walkill River 

 extends from Deckertown westward, and is chiefly formed of Hud- 

 son River shales or slate, which, according to Mr. Barton's later in- 

 vestigations, should be called in part Trenton.^ Under these, east 

 of Deckertown, is a blue limestone, and overlying them uncon- 

 formably on the west is the Kittatinny conglomerate, which forms 

 the ridge of that name and corresponds to the Oneida conglomerate 

 of New York. The dike comes out along the contact of the con- 

 glomerate and the slate. They have been spoken of as unconform- 

 able in the New Jersey Report for 1868, but this is a mistake. 



SECTION XX 



The ridge, as shown on the map (which is an enlarged portion of 

 the New Jersey topographical map sheet No. 1), forms a steep hill- 

 side some six hundred feet above the neighboring valley. No stream 

 of any size runs down its sides across the syenite, and only small 

 gulches afford exposures. The dike forms a great terrace, and is, 

 in its broadest part, 300-400 yards across. Its outcrop is marked 

 by a lineal succession of conical hillocks, with small gullies between, 

 making rough topography. A depression runs along the western 

 edge of the dike, and is somewhat wet. This marshy land effectually 

 conceals the western contact. On the north the dike runs out as an 

 easterly spur on the ridge. Evidences of its baking action on the 

 shales run further, but no eruptive rock appears. It terminates 

 with a steep hillside covered by loose fragments. At the southern 

 extremity the eruptive rock appears along the Brick House Road, 

 which crosses the mountain, but beyond the road it cannot extend 

 far, as a great precipitous cliff of conglomerate called Decker's Rocks 

 comes in and diagonally cuts off its course. No outcrops appear 

 at the foot of the cliff, and the float material is all baked shale and 

 sandstone. 



The dike varies considerably along its course. The tyjiical 

 elaeolite-syenite forms the northern third and the southern extremity, 

 but between these points its character changes. Near the northern 



1 N. H. Dartou. A. J. S., iii, xxx, 452, and xxxi, 209. 



