Study of the New York Obelisk as a Decayed Boulder. 99 



45° toward the north. Occasional large bunches of granular horn- 

 blende occur, elongated, with their major axes inclined to the N.N.E., 

 marking the original bedding plane of the granite. The microcline 

 crystals are often 1 inch long by ^ to | of an inch wide, with high 

 lustre on many fresh faces. Those of the white feldspar (oligoclase) 

 were occasionally bright, but, in larger part, dull and whitened. 

 However, I w^as rarely able to detect fine cracks in any of the feld- 

 spar, even on the old weathered surface. Near the bottom of the 

 shaft occurs a thin seam of hornblende-gneiss, several yards in 

 length, dipping sharply toward the north like the vein at the bot- 

 tom of the E.S.E face. 



On the N.N.E. face of the shaft, the feldspar generally looked 

 dull, except on small half inch cleavage-planes, here and there. 

 Many masses of hornblende occur, all of dull black color, but with- 

 out products of decay. A small bunch of pyritous material, nearly 

 2 cm. in length, was seen, blackened and dull. A large crystal of 

 white oligoclase, 2 cm. long, was covered with a dull white crust, 1 

 mm. in thickness. In and around the two cartouches of the second 

 row from the top, a large amount of hornblende occurs. At the 

 two cartouches of the third row, below the middle of the shaft, the 

 decay and dropping out of mica scales have caused much pitting of 

 the surface. 



On the E.S.E. face of the shaft, between the legs of the middle 

 bull, a streak of hornblende-gneiss occurs, 10 cm. in length, with a 

 dip of 35° to the north ; others are found in that vicinity, with the 

 same inclination. Most of the feldspar presents a waxy lustre (in 

 part due to the paraffin absorbed during the water-proofing treat- 

 ment in 1885), with occasional cleavage-planes of microcline^ show- 

 ing bright lustre ; in places, however, below, the feldspar is often of 

 brownish red rusty appearance. Between the two cartouches of the 

 second row, across the body of the owl, runs a black seam of horn- 

 blende-gneiss, two feet in length. A little above a lower cartouche, 

 in the north column, are rusty stains, like those from decomposing 

 pyrite; the feldspar grains are sprinkled with bright red spots; and 

 the surfaces of the oligoclase crystals are dull white and pitted. The 

 bottom of this cartouche is crossed by a lenticular black mass of 

 hornblende-gneiss, dipping about 40° to the north; smaller ones 

 occur beneath. Below this, fresh and bright surfaces of oligoclase 

 were noticed, but it was generally dull and whitened; and indeed 

 the feldspar planes, all the way down this side, are often softer and 



