Naf. Science at the Uuii: Minn. — N. H. WincheU. 165 
refers them to concretionary action. Dr. Sauer, while admitting 
the pebbles to be genuine "Gerolle," holds that the conglom- 
erate is altogether newer than the gneiss, and that it has been 
"folded and faulted in." Dr Credner suggests however, that 
such an explanation should not be adv*anced as a mere hypothe- 
sis, but ought to have some facts of observation to sustain it. 
He gives the occurrence a common sense interpretation when 
he says: "Especially significant for the sedimentary origin of 
the fundamental gneiss formation is the presence of conglom- 
erates embraced within it.^'f In this conception he includes 
not only cases where a conglomerate is distinctly embraced in 
a gneissic mass, but those where conglomerate terranes alter- 
nate with recognized crystalline masses. "In Canada" he re- 
marks, "we find a complex of beds over 300 meters thick in 
which rounded fragments of syenite and diorite, of greater and 
less magnitude, are held together by a quartzose binding 
medium rich in mica." "In Michigan," he says, "several con- 
glomerates formed of rolled fragments of gneiss, granite and 
quartzite are imbedded in an arenaceous talcose groundraass. 
In Vermont, is a similar zone of conglomerates; while near 
Konigsbergis a couglomeritic sandstone which alternates with 
gneisses and fundamental schists." 
The foregoing information has been assembled for the pur- 
pose of placing before geologists a body of little known and less 
considered facts which must be brought into account in every 
attempt to reproduce the history of the oldest known crystalline 
rocks. The facts appear to the writer most intelligible on the 
hypothesis of a sedimentary origin of such rocks; but it has not 
been his purpose to argue that view except so far as evidence is 
supplied by the presence of such conglomerates as have here 
been passed in review. 
NATURAL SCIENCE AT THE UNIVERSITY OF 
MINNESOTA. 
By N. II, WlXCHELL. 
The universities and colleges of higher gi-ade in the United 
States have in many instances begun as classical academies or 
* Lehmann Untcrsuchungen iiber die Entstelmng der altkryntallinfn 
Schiefergenteine, 1884, S. 128. 
t Credner, Elemente der Oeologu\ S. oT.".. 
