12 FRANK D. ADAMS 
of these bands being scapolite, pyroxene, some hornblende, some 
calcite, and a little microcline. A very small amount of sphene is 
also present in the rock. 
The analysis as given under No. 1 @ represents the composition 
of the specimen as collected; that given under No. 1 b represents the 
composition of the rock as it appears when the calcite present (deter- 
mined by calculation from the amount of CO, present and also by 
direct experiment) is deducted and the amount of the remaining 
constituents is recalculated on the basis of 100. No. 1 0 therefore 
represents the percentage composition of the silicated portion of the 
specimen, or, to put it in another way, it represents, except in the case 
of the lime, the additions made to the limestone by the granite magma 
in this first stage of alteration. ‘The specimen contains 34.50 per cent. 
of calcite, leaving 65.50 per cent. of silicates. ‘This silicated portion 
of the rock, as will be seen by comparing analysis No. 1d with Nos. 2 
and 3, bears a general resemblance in composition to the two latter 
rocks which represent the subsequent stages of alteration, the per- 
centage of silica being practically identical in all cases. 
No. 2 is the analysis of a typical specimen of the amphibolite which 
alternates with thin bands of the limestone at Maxwell’s Crossing. 
It represents a second stage in the alteration, this particular specimen 
being practically free from calcite. Under the microscope it is seen 
to be composed of hornblende and pyroxene, more or less completely 
replacing each other in the alternate bands, together with a consider- 
able amount of scapolite, plagioclase and untwinned feldspar. ‘The 
rock also contains many minute rounded grains of sphene scattered 
everywhere through it, but holds no iron ore and no biotite. 
No. 3 is the analysis of a harder variety, being a typical amphibolite 
and representing the last stage of the change. It occurs as an inclu- 
sion in the granite in the same series of exposures as that from which 
the other specimens were taken. The field relations show that it 
has been derived from variety No. 2 by further alteration. Although 
not differing much from No. 2 in chemical composition, under the 
microscope it is seen to differ considerably from it in structure, the 
individuals of the several constituents showing a less marked tendency 
to a rounded outline than in the case of No. 2. In mineralogical 
composition also it presents certain differences, the pyroxene and 
