512 J. F. KEMP AND J. G. ROSS 



ilmenite, perofskite, picotite, and apatite. Alteration products 

 are also much in evidence, but no melilite was discovered. The 

 dikes strike nearly north and south and are believed by Mr. 

 Matson, from their relations with the gentle folds and faults to 

 have entered near the close of the Paleozoic.! 



Three interesting bowlders have been found in the drift at 

 Aurora, Canandaigua, and Syracuse, apparently from not remote 

 sources. They are all obviously dike rocks of basic character, 

 and are in quite fresh condition. They are of unusual types, 

 each, however, differing from the dikes which have been found 

 in place. Full descriptions are given in the papers cited below. 2 



In southwestern Pennsylvania, 200 miles from Ithaca, the 

 dike occurs which is shortly to be described in this paper. In 

 Elliott Co., Ky., 200 miles farther to the southwest there occur 

 two dikes less than a mile apart and cutting the Coal Measures. 

 The dikes strike northwest and the eastern one sends off a long 

 prong to the northeast. The longest exposure is a little less 

 than a mile in length, and the greatest width is fifty feet. The 

 rock is a typical peridotite in which olivine is much the most 

 abundant mineral, constituting with the serpentine referable 

 to it, more than half the mass. With it are pyrope, ilmenite, 

 enstatite, biotite, and apatite in decreasing order among the 

 original components, and serpentine, dolomite, magnetite, 

 and perofskite (first determined as octahedrite) among the 

 secondary. 3 



ij. F. Kemp, "Peridotite Dikes in the Portage Sandstones near Ithaca, 

 N. Y.," Amer. Jour. Sci., Nov., 1891, p. 410. In this paper several earlier 

 local records are mentioned. P. P. Schneider, " Notes on Eruptive Dikes 

 near Ithaca, N. Y.," Proc. Onondaga Acad. Sci., I, 130, p. 1903. V. H. 

 Barnett, "Notice of the Discovery of a New Dike at Ithaca, N. Y.," Amer. 

 Jour. Sci., March, 1905, p. 210. G. C. Matson, "Peridotite Dikes near 

 Ithaca, N. Y.," Jour. Geo}., April-May, 1905, p. 264. 



2 J. F. Kemp, "A Remarkable Erratic from Aurora, N. Y.," Trans. N. 

 Y . Acad. Sci., XI, 1892, p. 126.' B. K. Emerson, " Notes upon Two Boulders 

 of very Basic Eruptive Rock from the West Shore of Canandaigua Lake , 

 etc.," Am. Rep. N. Y. State Mus., 46, p. 251, 1893. This eruptive had a 

 piece of Trenton limestone adhering to it and showing contact effects. 

 C. H. Smyth, Ir., "On the Syracuse bowlder," Amer. Jour. Sci., luly, 

 1902, p. 30. 



sj. S. Diller, "Peridotite of Elliott Co., Ky.," Bull. U. S. Geol. Survey, 



