374 Gratacap—Lozoonal Rock of Manhattan Island. 
that we must range the-formations of this continent under two 
separate categories, the nomenclature of each of which should 
be kept distinct, even after their contemporaneity may have 
been ascertained. Furthermore, correlations between the two 
categories should be based primarily upon phenomena observed 
or observable upon this.continent, for it is now evident that no 
foreign standard will be found adequate for this purpose. 
ArT. XXXVIII.—The Hozoona! Rock of Manhattan Island ; 
by L. P. Gratacap. 
A BED of serpentine rock bordering the western margin of 
New York Island between 55th street and 60th street, and 
now for the most part built over, some years ago awakened a 
momentary interest from its display of strips of ophio-calcite 
which resembled the eozoonal beds of Canada, and led to some 
surmises as to their organic character. This area of serpenti- 
nous rock, forming a band enclosed on the west and east by 
mica schists or a highly micaceous gneiss and limited south- 
ward by a broad outcropping of granite, is gradually disappear- 
ing from view and may at any time become an affair of local 
record. At present its best exposure is on the north side of 
59th street between 10th and 11th avenues, and it can be traced 
to near 56th street, by isolated knobs appearing above the level 
of the sidewalk and in back yards. It was recently uncovered 
to some extent when the cisterns for the immense gas-holders of 
Equitable Gaslight Company were being constructed, and some 
examinations then made both of the rock in place and of 
microscopic sections, may prove of interest in view of the gen- 
eral attention given to the discussion of the origin of serpentine, 
& discussion which seems to widen; and to which the later con- 
tributions by Dr. Becker* would seem to give a new impetus. 
This outcropping of serpentine is intimately associated with 
and intermingles with an acicular fibrous partially altered 
hornblende or actinolite, the hydrous anthophyllite of Dana. 
From this area were derived the numerons bowlders of this 
rock which are found to the south as far as the northern mar- 
gins of Long Island. Dr. L. D. Gale, as quoted by Mather,t 
describes this anthophyllite locality in the following words: 
“This rock extends from 59th street following the strike, which 
is N. 80° E.; varies from this to due north and south as far as 
63d street, where it dips down and disappears below the river. 
* Cretaceous Metamorphic Rocks of California, by G. F. Becker, this Journal, 
XXxi, p. 348. 
+ Geological Survey of New York, Pt. 4, p. 581. 
