NORTH AMERICAN GEOLOGY. 213 



The ore is found in a bed unquestionably iuterstratified with the crys- 

 talline rocks, and presents some evidence of having been originally in 

 granular form and sorted by shore action, as suggested by Julien.* 



72. In the midst of the Adirondacks, at Lower Saranac Lake, Brit- 

 ton notes the occurrence of a series of schistose gneisses with micaceous 

 and hornbleudic schists holding abundant quartz veins, and dipping 45 

 degrees north, and Julien calls attention in this connection to the simi- 

 lar series, bordering the Adirondacks, especially on their eastern side.t 



73. In a description of the Wallbridge magnetite mine in Canada, 

 Chapman discusses the Archean rocks of that district, and recognizes 

 four divisions, rather than the three proposed by Vennor. Two of the 

 series are thought to be volcanic, the others metamorphic, and it is 

 thought that the syenites should be separated from the lower stratified 

 gneisses. I 



74. The crystalline rocks extending southward from Westchester 

 County, N. Y., have received some attention in the literature of the 

 past year. At a meeting of the New York Academy of Science, New- 

 berry states his opinion that they are of Archean age; and Martin, in 

 calling attention to their great difference from the Highland rocks, and 

 their more hydrous condition, suggests that it may be due to a long 

 submergence at the bottom of the Trias basin. Britton states that at 

 Washington the series contains less feldspar and generally more mica 

 than in the Highlands. § 



75. Britton presents an additional note on the geology of Staten 

 Island. From the discovery of partially altered amphibole in the ser- 

 pentine, he is of opinion that the latter has been derived from horn- 

 bleudic or tremolitic strata, which have been found to a limited extent 

 on the island, and from magnesian limestone. He states that the strati- 

 fication of the rocks is unquestionable, and gives a number of dips. It 

 is thought that the serpentine does not form an anticlinal, as before 

 described, but probably a geosynclinal. As the serpentine of Hoboken, 

 Staten Island, and New York lie along the strike, it is suggested that 

 they may occupy a belt in the gneisses, and that their outcrops and 

 those of the limestones of New York Island may be due to pitch or to 

 cross faults. || 



76. Frazer, in a sketch of the geology of York County, Pennsylvania, 

 summarizes his views on the crystalline rocks of that district. None 

 of the rocks are thought to be Laurentian or Norian, unless, perhaps, 

 in a portion of the South Mountain. The lowest horizon appears to be 

 equivalent to the horizon of the Huronian, which is supposed to cover 

 most of the areas, and of which at least 14,000 feet is exposed in the 



* American Inst. Mining Engs., Trans., 1886. 



tNew York Acad. Sci., Trans., vol. 5, p. 72. 



}; Canada Royal Society, Trans., vol.3, sec. iv, pp. 23-26. 



§ New York Acad. Sci., Trans., vol. 5, pp. 19,20. , 



II Nat. Hist. Soc. of Staten Island, Trans., Oct., 1886. 



