43 



a tendency to decomposition. It is met with of this variety upon 

 the canal about two miles from Trenton, and in several places 

 further to the northeast, as far as the spot where the rock ceases 

 to show itself in place, which is about three and a half miles from 

 the town. It may be traced about two miles further, by observing 

 the character of the diluvium above it. 



Its economical importance consists chiefly in its including seve- 

 ral valuable varieties of building stone, well adapted to structures 

 demanding solidity and strength. Some of it would make a very 

 fine road-stone. To the scientific world it is interesting, as pre- 

 senting one of our few localities of zircon, which occurs about 

 fifty yards above the bridge at Trenton. The soil over this 

 formation is a very heterogeneous mass of diluvium, derived from 

 the gneiss and the formations to the northwest. It is generally 

 gravelly. In the valley of the Assunpink it is often a greenish 

 sand and gravel, derived from the quartz and hornblende, and is 

 then rather sterile. 



CHAPTER II. 



OF THE OLDER SECONDARY OR APPALACHIAN ROCKS. — GEOLOGY OF THE 

 KITTATINNY VALLEY, WITH ITS BRANCHES, AND OF THE REGION OF 

 THE KITTATINNY MOUNTAIN. 



Nature and Cojnposition of the Strata. — Having in the last 

 chapter described the general and local geology of the primary 

 districts of the State in as much detail as the limits of the present 

 work would permit, I propose, in the present place, to ofl'er a 

 similar account of the geological features and structure of the 

 region occupied by that extensive group of formations of exclu- 

 sively sedimentary origin, which I conceive to have been depo- 

 sited during the period that next succeeded the first elevation of 

 the primary strata. 



As these sedimentary rocks repose in immediate contact with 

 the gneiss, presenting, from the attitude of their beds, abundant 

 evidence that they were precipitated upon it while it was yet 

 only in part elevated above the waters, and, as the same strata, 



