44. WILLIAM J. MILLER 
dikes of hornblendite occur within the dikes of white plagioclase- 
rich material. These dikes of hornblendite are exactly like the 
ones above described. Lying in the midst of the fractured zone 
at this locality and parallel to its strike, there is a twenty-inch 
wide band of dark, highly foliated gabbro rich in ferromagnesian 
minerals (see Fig. 6). This band of dark gabbro cuts squarely 
across the curving, dike-filled cracks by sharp contact on one side 
and by moderately sharp contact on the other side. In the midst 
of the dark band and parallel to it there is a dikelike strip of white 
plagioclase-rich anorthosite several inches wide, separated into 
blocks by multiple faulting. These faults extend across the dike- 
filled fractures of the anorthosite-gabbro on one side. The dark 
‘band of gabbro with its faulted white strip is well shown in 
Figure 6. 
The history of the features which occur at the locality just 
described is probably about as follows. The main mass of the 
anorthosite-gabbro now at the surface was intruded and nearly or 
completely solidified. ‘Then it was subjected to a torsional strain, 
probably due to a moderate pressure externally applied, whereby 
the system of parallel curving cracks was developed. ‘The cracks 
were filled with plagioclase-rich dike material forced upward as 
a differentiate from a lower level of still more or less liquid gabbro. 
Still later came the intrusion of the hornblendite dikes into some 
of the same cracks, this material also having been produced as a 
differentiate at a lower level. Distinctly later, the twenty-inch- 
wide band of dark gabbro rich in ferromagnesian minerals was 
intruded, this material also having been derived from a portion of 
the general gabbro mass which was still in a more or less liquid 
condition at a lower level. ‘Then the small white dike was intruded 
into the band of dark gabbro. Finally, after the whole compli- 
cated mass of gabbro and anorthosite now at the surface was 
solidified, the band of dark gabbro with its small white dike and 
the adjacent rock on one side were subjected to multiple faulting 
on a small scale. 
A local portion of the fractured zone lying a few rods north 
of the road exhibits a high degree of crushing. Figure 7 gives a 
fair idea of this locality. The rock is mostly a very light-gray 
