Metamorphic rocks. 
475 
limestone, F. 11.* passing into the sandstone, and assuming near the passage a clear reddish 
hue and lastly, the belt of altered limestone in contact with a small elevated hill or dyke of 
felspathic sienite, the cause of the altered structure of the calcareous rock. All of these 
stratified masses, the gneiss, the sandstone, the blue limestone, and the white crystalline belt, 
dip alike towards the northwest at a gentle inclination. Graphite is here present as usual in 
the calcareous mass ; which besides contains other minerals. 
“ Portions of the altered rock are coarsely crystalline, though other parts of it are more 
minutely granular. A variety which is variegated with numerous blue shades of plumba¬ 
ginous mineral, might evidently, from its susceptibility of a good polish, be employed as an 
ornamental marble. 
“ Between the sienitic ridge here spoken of ,and another lying a short distance to the north, 
there occurs another smaller belt of the altered limestone, deeply buried between the primary 
rocks. At this spot some enthusiast in search of mineral treasures, expended at a former 
day no inconsiderable amount of time and labor, in excavations for silver ore in the sparry 
limestone. 
“ West of the last mentioned point may be seen, by the side of Panther pond, another still 
more unimportant exhibition of the altered sparry rock, not deserving of a special description.”! 
Mr. Nuttall, one of the most ardent naturalists of the age, and who has observed the geology 
of North America more extensively than almost any other individual, has described the lime¬ 
stone of the range under consideration. Describing the rocks near Mr. Fowler’s house at 
Franlilin, he says, “ The crystalline calcareous rock, which here alternates with granitines of 
felspar and quartz, or with beds of sienitic granite, disappears, and a confluent graU\vacke, 
almost porphyritic, and contemporaneous apparently with the other formations^ appears directly 
overlaid by a bed of leaden minutely granular secondary limestone, containing organic remains 
of the usual shells and corallines, and layers of blackish hornstone or petrosilex. This rock, 
as well as the grauwacke beneath^ presents disseminated crystals of blue fluate of lime. In 
the limestone the cavities are sometimes very numerous, and lined both with pseudomorphous 
masses and cubes of blue and white fluate and quartz crystals. 
'• “ Thus we have here before us, as at Lake Champlain, the novel and interesting spectacle 
of an union of every class of rocks, but passing decidedly into each other as if almost con¬ 
temporaneous ! If they are not contemporaneous, how do they happen to penetrate each 
other by veins ? Why do they present similar mineral substances ; similar organic remains ? 
Why do the same relics of plants occur over the anthracite of Rhode-Island (which is occa¬ 
sionally penetrated even by seams of asbestus), as over the bituminous coal-fields of Pitts¬ 
burgh and Richmond ? Why are the beds of coal at Richmond in Virginia penetrated by 
veins of granite ? ” 
“ Are, in fact, those supposed epochas of time, believed to have intervened between the 
production of strata, anything more than an imaginary distinction of formations really allied, 
und as strictly dependent on each other as the members of the same formation ? The grau- 
* The Mohawk limestone and Calciferous group of the New-York Geological Reports, 
t Final Report of the Geology of New-Jersey, by Prof, H. D. Rodgers, pp. 166, 176. 
