322 The American Geologist. November, 1S94 
the pyroclastic layer being above the spheroidal basalt. The 
diabase and the basalt, although they differ remarkably, are 
considered to be equally basic eruptive rock, the former cool- 
ing as an intrusive in older rocks and the latter as a surface 
flow. The pyroclastic stratum reposes upon an uneven sur- 
face of spheroidal basalt. It is composed of fragments of a 
light gray aphanitic amygdaloidal rock similar to that form- 
ing the spheroids below it, and ranging in size from the frac- 
tion of an inch to a foot or more in diameter, the average size 
being about three inches. "These fragments are finely com- 
minuted volcanic ejectamenta. In general the fragments are 
more or less rounded, but sharply angular fragments are also 
abundant." 
In the spheroidal basalt are some curious and interesting 
features. The large spherules are sometimes elongated, bale- 
like masses, whose longer axes are about parallel and extend 
obliquely downward. They sometimes weather out near the 
center, leaving a shell. They are amj^gdaloidal porphyritic, 
with feldspar, and in some cases the same rock embraces many 
fragments of red jasper. The interstices between the spher- 
oids are filled with comminuted fragments of rock of the same 
kind, but decayed and crumbling, or with secondary products. 
In one case a block of sandstone four feet in diameter was 
seen resting partly imbedded in the volcanic rock. In thin 
section these spheroids display simply a uniform, finely crys- 
talline, or porphyritic and amygdaloidal rock, composed of 
lath -shaped feldspars and a considerable proportion of glass, 
with secondary formation of much calcite and chlorite, and 
sometimes quartz. In the large spheroids the center is less 
amygdaloidal than the rest of the rock. 
The author considers the evidence warrants the conclusion 
that the spheroidal portion of these, rocks was ejected as a 
surface flow and that the rounded spheroids are an incident of 
flowage after ejection. The pyroclastic layer he regards as of 
the nature of volcanic ash, projected from a crater which was 
probably at some distance to seaward. 
Note. This paper throws considerable light on some prob- 
lematic features seen in connection with the greenstones of 
the Archean in the lake Superior region. It appertains to 
the spheroids and to the jaspers of the sandstones. Spheroidal 
