MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK T3 
Westchester and Putnam counties in southeastern New York, with 
the idea of determining the limits of the series of rocks associated 
conformably with the limestone of the Green Mountain region. 
Since the fossils of the limestone had been found only in Vermont, 
Dana, in order to extend his conclusions to the rest of the Green 
Mountain region, thought it necessary to prove that the Vermont 
limestone must be the same stratigraphically as the limestones of the 
region to the south. Dana spent over 2 years in the study of this 
area, nor were his studies confined to the limestones of the region; 
they embraced the gneisses and schists as well, and included a dis- 
sertation on the Cortlandt series of basic eruptives near Peekskill. 
His views are set forth in a series of papers entitled “ The 
Geological Relations of the Limestone Belts of Westchester County, 
New York,” appearing in the American Journal of Science during 
1880 and 1881 (op. cit.). That so brilliant a geologist as Dana 
should arrive at such a remarkable conclusion with respect to the 
origin of the Cortlandt series, namely, 
“ They appear to sustain fully the following conclusions: 
“(1) These rocks, although they include soda-granite, noryte, 
augite-noryte, dioryte, hornblendyte, pyroxenyte, and chrysolitic 
kinds, are not independent igneous rocks erupted from great depths. 
“(2) However complete their former state of fusion or plasticity 
may have in some cases been, they are metamorphic in origin. 
“(3) The strata that underwent the metamorphism were one in 
series and conformability with the adjoining schists and limestone, 
and were part of the Westchester limestone series.” (op. cit., 20, 
p. 219), may have been due to preconceived conclusions overriding 
observed field relations. Dana evidently was somewhat doubtful of 
his own interpretation, however, for in a succeeding paper (op. 
cit. 22, p. 103-19) he again discussed this same series of igneous 
rocks and commented on three possible sources of the clastic material 
which he thought made up the “original beds” (p. 110): “ (1) 
detritus from the Archean highlands; (2) igneous eruptions, afford- 
ing volcanic or igneous débris, in addition to ejected liquid rock, 
and along with more or less Archean detritus; (3) detritus from the 
Highlands, supplemented by ingredients from the ocean.’ Con- 
cluding, finally, that after a survey of the facts, the massive 
structures and crystalline characters of the rocks of the Cortlandt 
series, and the presence among them of hornblendic and augitic 
kinds containing soda-lime feldspars, and of even olivine-bearing 
basic rocks, should not militate against his previous conclusion, 
