Limestone Belts of Westchester County, N.Y. 208 
at the junction of the schists of Cruger’s Point with the soda- 
granite, where the schist itself bears evidence of partial fusion 
and exhibits other contact-phenomena. 
The proof of the crystallization of the rocks from a more or 
less perfect state of fusion or plasticity is thus complete. 
2. Evidences as to condition of fusion. 
But, admitting fusion or a plastic condition, the question 
still remains : 
ere these once-fused rocks fused approximately in satu, 
that is, where, or near where, they n e; or were the 
exotic? . 
a. The results are partly the same whichever the condition of 
JSusion.—If they were fused where approximately they now lie, 
that fusion must have come from accessions of heat, and such ac- 
cessions may have resulted from the movement and friction con- | 
nected with an upturning of the rocks; and it may hence have 
been one of the results, in that region, of metamorphic action 
at an epoch of general metamorphism ; and if so, at the very 
time that these rocks became fused or plastic through the 
process, other rocks of the region, owing to less extreme met- 
amorphie action, or to less fusibility, may have been left with 
their bedding unobliterated; just as much granite in New 
England and other countries received its crystalline condition 
in the same process and at the same time with the associated 
schistose rocks, the gneisses, mica schists, etc. 
All the facts as to fusion which have been presented are 
consistent with either mode of origin, even to the inclusions 
and the dikes or veins. 
(1) The veins or dikes have the same essential characters 
whether made one way or the other. As bas often happened 
in the case of granitic rocks, and even granular limestone, the 
fused or plastic material, under the pressure attending the sub- 
terranean movements, would have entered and filled all fissures 
that might have been opened to it, and so have made veins or 
dikes having the sizes of the fissures were they large or small, 
and possessing also a uniformity of grain like that of ordinary 
erupted rocks.” 
(2) Again, whatever the process of ejection, fragments, large 
or small, of any rocks adjoining such fissures might. have 
become included in the fused or plastic material. 
ge 0), veins of this kind are called 
veins of plastic injection, an abbreviation of the full statement that they were 
made by the injection of material rendered plastic or fused during a process of 
