67 



Following the range of the crystalline limestone somewhat 

 more in detail, we shall commence our description of its geologi- 

 cal features where it first conspicuously shows itself, in the neigh- 

 bourhood of Amity, in New York. Here, and for several miles to 

 the southwest, the belts of altered rock occupy a very considerable 

 width, in the valley ranging from Mounts Adam and Eve towards 

 Hamburg, forming a zone averaging, at first, half a mile in breadth, 

 but contracting to two or three hundred yards. The crystalline 

 material in its most perfect form, docs not, however, fill the whole 

 space, but occupies ratlier a series of closely adjacent parallel 

 bands, most numerous towards the middle and northwestern side 

 of the valley, where a chain of low irregular ridges usually con- 

 tain the limestone in the highest state of crystallization. These evi- 

 dently mark tlie existence of a series of parallel veins of igneous 

 origin, the intrusion of which into the limestone, have obviously 

 caused its alteration. Between the base of the Wallkill Mountain 

 and the crystalline rock towards the middle of the valley, we 

 usually meet with beds of the formation which evince but a par- 

 tial amount of change from the igneous action; the limestone 

 retaining more or less of its bluish tint, and presenting only a sub- 

 crystalline, or even the ordinary earthy, texture. These less al- 

 tered beds, reposing upon the gneiss of the Wallkill Mountain, dip 

 towards the northwest. Towards the base of the Pochuck Hill, 

 on the other side of the valley, the limestone would seem to have 

 undergone a more extensive alteration. Approaching Hamburg, 

 the crystalline belt contracts considerably in width. About two 

 and a half miles northeast of that village, we find it occupying a 

 broken chain of long, narrow, irregular ridges of considerable 

 elevation. These range parallel with the base of the Pochuck 

 Mountain, separated from it by a tract of low meadow ground, 

 about three hundred yards in breadth. In this belt the altered 

 limestone is in great confusion; the calcareous crystalline matter 

 being mingled largely, in many places, with a white friable sand- 

 stone, referable, obviously, to Formation I., the position of which, 

 when it occurs at all, is immediately beneath the limestone. 

 The fused calcareous matter seems in some cases to have pene- 

 trated the substance of the sandstone. The height of this ridge or 

 chain of ridges may be stated to average about two hundred feet ; 



