1892. | NEW YORK ACADEMY OF SCIENCES. 127 
it. The rarity of these varieties is the warrant for the mention of 
a boulder whose home is unknown, but which it is to be hoped may 
be traced. The rock is formed by a dense grayish-black ground- 
mass, through whieh are thickly set great crystals of black horn- 
blende and augite up to an inch or more in length, and at least half 
as much in width. In thin section the ground-mass proves to be 
glass, which is filled with minute colorless augites, about 0.1 mm. 
and less in breadth, and several times as long. The large horn- 
blendes are golden-brown, parallel to ¢ and b, and faint yellow, 
parallel to 4. They fuse easily before the blowpipe with a strong 
sodium flame. The cleavage angle, as kindly determined by Mr. 
A. 8. Eakle at the writer’s request on a No. II Fuess Goniometer, 
is 123° 55’, and the signals were good. This would indicate 
arfvedsonite, the soda amphibole, and the cleavage angle is the 
same as that originally given by Brooke. There is also a cleavage 
parallel to the plane of symmetry, but it is less perfect. In the 
rock the crystals are bounded by the prism and this pinacoid. They 
are also faintly zonal, the border being a darker brown. The 
augite is eight-sided and almost colorless. There are some very 
doubtful olivine remains. Of all the rocks described, the sty Gia 
which occurs with the elaeolite-syenite near Little Rock, Ark., 
nearest to this. The source of the boulder is probably in the Re T 
line Archean rocks to the northeast, and it has probably come from 
the Adirondack heights. The nearest exposure of these is distant 
a hundred miles at least, but of their petrographic character we 
know only in the most general way. It is also to be noted that 
peridotite dikes have been recorded in the interval, at Syracuse,! 
Manheim Bridge,’ and south of Aurora at Ithaca. Some undis- 
covered dike may have yielded the boulder. Professor Freley also 
gave the writer a piece of a small boulder that is a most excellent 
syenite. It indicates this rather unusual rock as existing in the 
northern crystallines, and increases the interest which should be 
felt in the study of the western Adirondacks. 
re 
Notes on Several Rocks Collected by E. E. Olcott, E.M., near Gold 
Hill, Tooele Co., Utah. <A series of rocks has lately been placed 
in the hands of the writer which was collected by Mr. Olcott on 
the western border of Utah, in the American Desert or on its con- 
fines. They are of sufficient interest in one or two instances to de- 
serve mention. S. F. Emmons, of the 40th Parallel Survey, has 
recorded some notes of this region as it lay within his explorations 
1G. H. Williams, The Serpentine (Peridotite) occurring in the Onondaga 
Salt Group at Syracuse, N. Y. A.J.S., Aug. 1887, p. 137. 
2 C. H. Smyth, Jr., A Third Occurrences of Peridotite in Central New York ; 
id. April, 1892, p. 322. 
3 J. F. Kemp, Peridotite in the Portage Sandstones near Ithaca, N. Y.; id. 
Noy. 1891, p. 410. 
