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fore, with the lower margin of the formation, about one rnile 

 northwest of Trenton, we find a well marked belt of strata occu- 

 pying a breadth of about two miles, between that point and 

 Hill's Creek, its northwestern limit. This consists of conglome- 

 ritic sandstones of the kind above referred to. 



The materials of this lower set of rocks are pebbles and grains 

 of sand of the same minerals which compose the primary strata, 

 upon the upturned edges of which these rest. The rounded 

 fragments are from the size of coarse sand to an inch in diameter, 

 and comprehend grains and pebbles of quartz, some of which are 

 of the semi-transparent, partially opalescent kind, pretty abundant 

 in certain strata of the gneiss. Associated with the quartz there 

 is much felspar, white or yellowish, and partially decomposed; 

 also, a small share of mica and a considerable quantity of horn- 

 blende. Throughout some of the strata there is a greater or 

 less proportion of hydrated oxide of iron, dispersed in minute 

 yellow specks. The decayed condition of the felspar, and the 

 stains from the oxide of iron, impair to some degree the value of 

 these rocks for the purposes of architecture. The dip of the 

 beds is to the northwest about 20°. A want of parallelism in 

 the planes of stratification, and some minor irregularities, inter- 

 fere with the value of many of the quarries in this range, by 

 preventing that uniformity of structure which building stone, 

 for many purposes, must have. A good display of these rocks, 

 in all their distinctive features, is to be witnessed in Dean's 

 Quarry, a mile and a half from Trenton, upon the feeder of the 

 canal. The same varieties show themselves on the Delaware 

 and Raritan Canal, about six miles northeast of Trenton, where 

 the beds agree in all particulars with these inferior strata along 

 the Feeder. 



Overlying these more heterogeneous rocks at the bottom of the 

 formation, there succeeds a belt of a somewhat different character, 

 having a breadth of about two miles, from Hill's Creek to the 

 stream at Abner Scudder's. The prevailing rock is a coarse- 

 grained pinkish sandstone, consisting of transparent quartzose sand, 

 with numerous white grains or specks of somewhat decomposed 

 felspar, and small flattish pebbles or flakes of the more argilla- 

 ceous kind of red sandstone. The chief ingredient in this rock 



