112 J. D. Dana— Origin of the Rocks of the Cortlandt Series. 
chrysolitic!hornblendyte are in united layers each only an inch 
or two thick ; and (4) there are transitions into mica schists not 
thus easily explained. 
hese objections appear to prove that the rocks are not truly 
eruptive. But they do not make it sure that they have not 
originated in depositions of vol- 
eanic debris or cinders (lapilli, 
badly called ‘voleanic ashes”), 
u 
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tive rocks; (2) mixtures of the 
extremest kind observed might 
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o. 
abrupt transitions from  cinder- 
made beds to those of ordinary 
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sediments might result, even to the intercalation of a layer 
limestone or mica schist, or magnetic iron, or emery, 
ures presented by the rocks described ; and even if, in the pro- 
cess, the heat had not reached that of fusion, portions of the 
beds permeated with heated moisture might. have become 
