490 A. A. JULIEX AMPHIBOLE SCHISTS OF MANHATTAN ISLAND 



No chemical analj^sis has ever been recorded * of the massive serpeii- 

 tine-like rock of this locality, the attention of mineralogists and chem- 

 ists having been mainly attracted to the '' hydrous anthophyllite," which, 

 as first shown by Dana,t represents the original actinolite in condition 

 of hydration, preceding the process of serpentinization. The first three 

 of the following analyses exhibit the process of this change : 



XXXV. " Hydrous anthophyllite " (mean of two analyses). West Fifty-ninth 



street. Smith and Brush. 

 XXXVI. " Asbestiform mineral found associated with chlorite. New York 

 island." Doctor Thomson. 

 XXXVII. " Hydrous anthophyllite." Boulder found at East Forty-ninth street, 

 near Madison avenue. C. A". Joy. 

 XXXVIII. Serpentine. Aqueduct shaft 26. Catlett. 



SiO, 



FeA 

 FeO . 

 MnO. 

 CaO . 

 MgO . 



Na20 



XXXV. 



58.33 

 Trace.... 



8.76 



29.34 

 Trace.... 



.88 

 2.26 



99.57 



XXXVI. XXXVII. XXXVIII 



54.98 

 1.56 

 9.83 



1.20 



13.38 

 6.80 



11.45 



99.20 



46.43 



9.38 



1.38 



5.06 



28.80 



8.58 



99.63 



39.92 

 .08 

 .50 



.90 



42.52 



CO2 1.64 



14.62 



100 18 



At West Fifty-ninth street a portion of the '" hydrous anthophyllite " 

 layer was occupied by irregular greenish masses, made up apparently of 

 serpentine, calcite, actinolite, tremolite, chlorite, and talc, which have 

 been described by S. Akerly (1819), L. D. Gale (1839), I. Cozzens (1843), 

 and Mather (1843). More recenth^, Gratacap has described the " seam- 

 like bands of ophicalcite of irregular thickness, expanding and con- 

 tracting, and sporadically occupied nests or spots inclosed in the sur- 

 rounding rock; the bands rising and falling as if they had undergone 

 plication, as in the folded gneiss layers of the island." J Toward Sixty- 

 third street the amphibolite became richer in talc, associated with much 

 chlorite, passing in part into steatite. Along the east side of the bed, 

 near its contact with the gneiss, a layer of quartz rock attracted the at- 

 tention of the earlier observers — perhaps simply a more quartzose layer 

 of the gneiss. 



*The analysis of serpentine attributed bj-^ Nevvland to Doctor Thomson is evidently, by some 

 oversight, an inexact copy of Joy's analysis (xxxvii) of "hydrous anthophyllite." 

 t Am. Jour. Sci., vol. xx, 1880, p. 31. 

 + Am. Jour. Sci. (3d series), vol. xxxiii, 1887, p. 373. 



