270 TRANSACTIONS OF THE [May 18, 
from interbedding or intrusion, but the latter explanation is 
strongly indicated both by the exposures themselves and by 
analogy with other localities. When this locality is compared 
with those where the minerals are clearly the product of contact 
metamorphism, decided differences appear. The light-gray 
amphibole is a new factor; the scapolite is absent, and the py- 
roxene is of a light-green color and, from its superficial proper- 
ties, would be classed as diopside. The pyroxene of the other 
localities is, on the other hand, dark-green or black, and de- 
cidedly augitic in aspect. Whether or no such differences as 
these point to a decidedly different origin cannot, as yet, be 
positively stated, but on @ priori grounds it seems very doubt- 
ful that they do. Variation in the character of the intrusive 
rock and of the limestone would certainly seem a sufficient 
cause; while some localities, as yet undeveloped, show an asso- 
ciation and habit intermediate between the extremes described. 
To sum up briefly the leading facts presented above: Py- 
roxene, phlogopite, scapolite, titanite and feldspar, together with 
apatite, tourmaline, wollastonite, quartz and zircon, often occur 
together, and in several instances they are clearly a product of 
contact metamorphism. 
Generally the intrusive rock is of intermediate composition, 
while the rock which it cuts is limestone. 
In all of these cases it seems clear that heated solutions and 
gases have been the immediate agents of mineral formation. 
Several of the above-named minerals also occur with light- 
gray amphibole on the contact between gneiss and limestone, 
and while the evidence is not conclusive it is probable that they 
are formed in the same way. In other cases it is possible that 
minerals on gneiss-limestone contacts may be a product of 
regional metamorphism. 
Finally, a similar association appears when there is no other 
rock than the limestone shown. For such occurrences it is only 
possible to infer their origin from their resemblance to more 
clearly defined examples. 
In conclusion, it should, perhaps, be added that if there ap- 
pears to be, in the foregoing pages,an attempt to exaggerate the 
importance of contact metamorphism as a source of minerals, it 
is simply due to the fact already stated, but possibly not suffi- 
ciently accentuated, that this paper aims to consider only the 
single class of mineral occurrences which are certainly, or possi- 
bly, of this type. 
HAMILTON COLLEGE, CLINTON, N. Y., June, 1896. 
