42 The American Geologist. Tulv - 1905 
along the north side of the Blue hills. It exhibits in a good 
degree the characters of a true hornstone ; but it is no- 
where of flinty hardness ; and the fact that it is never visibly 
micaceous testifies to the essentially non-alkaline character 
of the sediment. As a rule, the stratification is hopelessly 
obscure ; but at a few points, which are so distributed as to 
cover practically the entire group of ledges, it is fairly dis- 
tinct and entirely unequivocal. The attitude of the bed- 
ding is, as usual in the Cambrian of the Boston basin, very 
constant, with east-west strike and vertical dip. 
The essential relation of these sediments to the com- 
plex is clearly indicated, not alone by their metamorphic 
character, but also by typical igneous contacts with the 
fine granite and quartz porphyry of the contact zone, and 
irregular dikes or apophyses of the quartz porphyry and 
more regular dikes of normal felsite. 
BODY OF THE BATHOLITB. • 
Normal Granite — This is a coarsely crystalline aggre- 
gate of feldspar and quartz, chiefly, with a small propor- 
tion of a dark constituent regarded by Dr. Bascom as chlo- 
ritized. amphibole. The feldspars, according to this author- 
ity, include orthoclase, commonly of a pinkish tint due to 
oxidation, and a lime-bearing albite in which the greenish 
tint due to epidotization is more or less marked. The an- 
alysis shows an acid rock, similar to the normal granite of 
the Blue hills, but rather more basic and richer in plagio- 
clase, though poorer in the ferrp-magnesian constituent. 
The outcrops of normal granite are chiefly confined 
to two rather irregular areas ; and the general relations of 
these to the complex is not central, as might seem most 
natural, but peripheral. They form, respectively, the 
northern and southwestern borders of the complex, and 
converge but, apparently, do not meet, to the northwest- 
ward, in the vicinity' of Grove and Center streets. The dis- 
positions of the normal granite is such as to suggest at 
once a general monoclinal or shallow synclinal structure for 
the complex, — the surface of the normal granite forming a 
trough the axis of which pitches to the southeast, thus 
allowing the normal granite to slope southward and north- 
eatsward beneath the contact zone of fine granite and 
