136 Thirty-second Report on the State Museum. 



South of the mines along the line of Mill brook, extending from Port Henry 

 to the neighborhood of Ensign pond, we find the Laurentian limestone group 

 with its rusty, decomposing, syenitic rocks and some sulphury ores. This lime- 

 stone is undoubtedly a newer series than that of the Mineville rocks, being 

 clearly proven to rest unconformably upon the Lower Laurentian rocks of the 

 Cheever Ore Bed, from which neighborhood it extends along the lake to 

 Port Henry, thence westward to vicinity of Ensign pond. It encircles the end 

 of the lake range, of which Bald Peak is the highest mountain, north of Port 

 Henry. 



The dips of the limestone group are more gentle, as a rule, than in the lower 

 division, and, as a whole, it has the appearance of having been deposited second- 

 ary to the Lower Laurentian, and unconformably upon it. 



The southern and southwestern portions of the township of Moriah are occu- 

 pied by a series which bears a doubtful relation to the magnetic ore ranges, but 

 is apparently intimately in connection with the limestone group. In some por- 

 tions it resembles the quartzites of the Lower Laurentian, and in others it re- 

 sembles more closely the light-colored garnetiferous rocks, which form a portion 

 of the lake range in the southern and eastern quarters of the township of West- 

 port, and belong to the Labrador series. The succession is, however, very dif- 

 ferent, and it is therefore impossible to identify them as the same. This group 

 is undoubtedly a continuation of the thinly bedded quartzites and syenitic rocks 

 which extend southward through Crown Point into Ticonderoga, where there are 

 numerous deposits of sulphury iron ores and plumbago. 



This group is characterized by its numerous Trap Dykes, apparently more 

 frequent in the vicinity of the limestone, though this frequency may be due to 

 the contrast in the rate of disintegration — the limestone leaving the trap rock 

 more boldly exposed. 



The line of junction between the two groups — the Lower Laurentian con- 

 taining the large deposits of magnetic iron ore, and the crystalline limestones 

 with the succession of quartzose rocks and garnetiferous gneisses — is not 

 clearly seen at any point. The reason of this is that along such lines of junc- 

 tion the action of the weather has had fuller force, and the decomposition and 

 disintegration has been more rapid, thus forming deep depressions and valleys 

 which have recently been filled by the glacial debris swept into them by the 

 moving ice. 



The limestone group, with its various associated rocks, may be said to occupy 

 the entire southern half of the township of Moriah, extending northward to the 

 general line of Mill brook from Ensign pond to Moriah Center, and from thence 

 in an easterly direction to the lake, and bordering the lake as far north as the 

 Cheever Ore Bed. 



The limestone is overlaid in many places along the lake by the Potsdam 

 sandstone, which is well exposed at and above Port Henry ; there are also fine 

 exposures of it in the northeastern corner of the township. 



The actual junction or overlapping of the Potsdam sandstone or quartzite on 

 the gneiss and limestone is nowhere to be seen. The reason is that the lime- 

 stones disintegrates so rapidly that the sandstone becomes undermined, and 

 breaking off, covers up the junction. 



The limestone along the lake extends westward to the base of the high range 

 which rises about 3,000 feet, in Bald Peak mountain, above the lake. The 

 rocks of this range, as far as my observations carry me, pitch to the westward 

 within this township, and probably belong to the Lower Laurentian, though they 

 have not been proven to contain any large deposits of magnetic ore. 



I would remark here that this range has never been carefully studied ; but I 

 hope to complete the township map now in progress, and prove the relations of 



