iVew Features in Geology of 2Iinnesot(i . — Winchell. 49 
massive acid rock originally, which cut the rocks of the iron- 
bearing formation. Subsequently they suppose that this 
massive rock has been presssed and broken and sheared. They 
suppose three or four directions of shearing in order to cut 
the rock into cuboidal blocks along certain planes of movement 
and a continued frictional movement along the same planes 
after the rock was cut, thus breaking off the angularities of 
the blocks and surrounding them by a matrix which they po- 
etically style the "flour of attrition." When sufficiently round- 
ed the blocks and the flour were then consolidated and became 
the Stuntz conglomerate. 
Our party carefully reviewed the whole subject. They not 
only found that the rock is a true conglomerate, but also dis- 
covered its basal contact on the iron-bearing formation. In- 
stead of being associated with the iron-bearing formation, and 
older than the slates and the graywackes, it is of the same 
formation as the slates and graywackes, and lies unconform- 
ably on the iron-bearing formation. We also found that the 
composition of the conglomerate is not uniform — as it must 
be if it have the origin presumed by the authors of that hy- 
pothesis. Not only do the felsyte pebbles var^;- in grain, even 
those in contact in the mass, some being porphyritic and oth- 
ers not, some being of a darker color lying beside those of a 
light color, but they are of different sizes, though in contact, 
rendering the shearing and cutting motion if it took place, 
one of multiple planes instead of definite ones, and of short 
and varied application instead of continued and rigid. 
W"e also found, what is most convincing, that the bottom of 
this conglomerate, when it lies on the jaspilj^te of the region 
is composed almost entirely of fragments from the jaspilyte. 
Messrs. Smyth and Finlay admit that, on their hypothesis, 
the intrusion oC the acid eruptive may have torn from the 
strata through which it passed, fragments of the jaspilyte, 
and might even carry them some distance in the direction of 
the flow. It is in that manner that they account for frag- 
ments of the jaspilyte which tiie}^ found in the conglomerate. 
That may be admitted. But we found the conglomerate to 
consist, in the proportion of 9 to 1, of fragments of jaspilyte 
at a point 10 feet from the contact. It is hard to believe that 
an acid rock composing but one-tenth of a mass would be able 
