244 J. F. KEMP — ROCKS OF THE EASTERN ADIRONDACKS. 



In 1871 T. S. Hunt gave a general review of the mineralogy of these 

 limestones and to some extent of the stratigraphy, and they were called 

 by him Laurentian, but as all the crystalline limestones from southern 

 Pennsylvania to northern Canada are sweepingly included, his conclu- 

 sions as to stratigraphy are open to criticism.* In 1883 Dr. Huntf ad- 

 vanced the view that the extended exposures near Port Henry represent 

 a great calcareous veinstone. 



C. E. Hall,| in 1879, made of those in Essex county one of the four 

 divisions of the Laurentian, and assigns them a later age than the Norian. 



G. P. Merrill,§ in 1889, and again in 1890, described the petrography 

 of the ophiolites and traced the serpentine to an original pyroxene. 



R. Pumpelly,|| in 1890, before this Society, cited the great lumps of 

 underlying gneiss included in the limestones, and explained them as 

 formed first by secular disintegration, after which they were involved in 

 the deposit of the limestone in and around them upon an encroaching 

 shoreline. 



Van Hise, Walcott and Pumpelly,^ in the same year, made a general 

 reconnoissance of the eastern side of the mountains, upon the study of 

 whose Paleozoic sediments Walcott had been long engaged. Van Hise, 

 with G. H. Williams,** also visited the eastern side and concluded that 

 the limestone rested on gneiss and was penetrated by intrusions of an- 

 orthosites. 



On the west side, however, the most extended work has been done by 

 C. H. Smyth, Jr., ft to whom we are already indebted for several papers 

 on the local geology. They are the most important of the contributions 

 made in late years. As previously stated, the crystalline limestone is 

 more extensive and better preserved than on the east, and is also pro- 

 vided with the same serpentinous associate or ophicalcite.JI Professor 

 Smyth leans to the unconform ability of the limestone upon the gneiss, 

 although emphasizing the obscure character of the phenomena and the 



* Mineralogy of the Laurentian Limestones. Twenty-first Ann. Rep. New York State Cabinet, 

 1871, p. 47. 



f Geology of Port Henry, New York. Canadian Naturalist, 1883, p. 420. 



X Laurentian Magnetic Iron Ore Deposits in Northern New York. Thirty-second Ann. Rep. New 

 York State Cabinet, 1879, p. 133. 



§ Ophiolite of Thurman, Warren County, etc. Am. Jour. Sci., March, 1889, p. 189. 



Serpentinous Rocks of Essex County, New York, etc. Proe. U. S. National Museum, vol. xii, 

 1890, p. 595. 



II Relation of Secular Rock-disintegration to certain Transitional Crystalline Schists. Bull. Geol. 

 Soc. Am., vol. 2, 1890, p. 218. 



^ Bulletin 86, U. S. Geol. Survey, 1892, p. 898. 



**Idem. 



ft Geological Reconnoissance in the Vicinity of Gouverneur. Trans. New York Acad. Sci., vol. 

 3[ii, 1893, p. 97. Petrography of Gneisses, etcetera. Idem., p. 203. 



IX The name ophicalcite is here used in preference to ophiolite, for the latter is merely a Greek 

 equivalent of serpentine, while ophicalcite means a serpentinous limestone. 



