New Features in GeoJocjy of Minnesota. — Winchell. 43 
stances the igneous underlies the sedimentary, and from it the 
sedimentary strata dip in all directions. Mr. Lawson cites 
many instances in which the sedimentary strata are penetrat- 
ed by the igneous, and in which blocks from the sedimentar}^ 
have become separated from their parent masses and carried 
some distance in the mass of the igneous, remaining surround- 
ed by the igneous after solidification, till the present, attest- 
ing their prior existence. He did not, however, attempt, so 
far as known, to assign an origin to the igneous Laurentian, 
except the general one of saying it is an igneous rock. When 
he saw numerous alternations of the sedimentary and the igne- 
ous, in parallel strata, however fine the sheets were, he ex- 
plained such alternations by assuming that the sedimentary 
strata had been split numerously, along the lines of easiest 
separation, and that into the openings the igneous rock had 
been forced. Without attempting to enumerate at this time, 
the insuperable obstacles that present themselves to this idea, 
I will call your attention to the facts that have lately been 
noted with care on the northwestern shores of Vermilion lake. 
They seem to demonstrate two important facts in the genesis 
of the Laurentian, so plainly, that any competent geologist who 
examines the field relations will be convinced of their signifi- 
cance, and of the correctness of the conclusions drawn from 
them. These conclusions, already intimated, are as follows: 
1. The sedimentary Laurentian is a crystalline condition 
of sedimentary strata which are conformably' a portion of the 
crystalline schists. 
2. The igneous Laurentian is the result of a more intense 
metamorphism, carried even to fusion of some strata. 
The parties of the survey have passed many times through 
Vermilion lake. They have uniformly noted the marked sed- 
imentar}^ structure continuing from Tower northward, along 
the islands and shores, passing from the Keewatin to the crys- 
talline schists without any interruption of the conformity of 
the strata. There is no break in the series. The crystalline 
character comes on gradually. The first important appear- 
ance of mica schist is on some of the small islands and on the 
coast which strikes across the southwestern part of T. 63-16, 
and into sections 35. and 86, of T. 63-17. This is at a distance 
of about three miles from the point where igneous granite 
