156 Conglomerates in Gneissic Terranes — A.WinchelL 
The most extraordinary occurrence of all is found on a small 
island which I named Wonder island, near the south-east shore 
of Saganaga lake, and supposed to be located a short distance 
beyond the international boundary.* This island lies far within 
the gneissic region. The contiguous main shores are charac¬ 
teristically gneissic. On the south I have traced the gneissic 
terrane eight miles, to its culmination in the Giant’s range and 
its southern limit near Gunflint lake; on the southwest, nearly 
to Frog-rock lake, twelve miles; on the west, to Oak lake r 
twelve miles; on the north, to the north shore of Saganaga lake, 
six miles. The point is therefore several miles from any bound¬ 
ary of the great mass of the Saganaga gneiss. 
At this place rounded pebbles are accumulated in sueh abund¬ 
ance as to constitute a real conglomerate. Two patches are ex¬ 
posed to view and disappear beneath the level of the water. 
One of the patches as far as exposed, is four feet wide, and the- 
other three. The breadth of the intervening gneiss is about ten 
feet. In neither are the pebbles generally in contact. In one 
area, the conglomeritic condition disappears gradually around 
the margin; in the other, somewhat abruptly—except that a 
single pebble is quite separate. The intervals between the peb¬ 
bles are filled with the common gneissic material in full posses¬ 
sion of its usual characters. The pebbles are of all sizes up to 
four or five inches in diameter; and they are generally dark 
green in color. Mineralogically, as far as I could judge in the 
field, they consist principally of the following species and varie¬ 
ties: Lamellar augite in coarse agglomerations; lamellar augite 
in fine agglomerations, with a minute quantity of light feldspar 
disseminated in strings and grains; lamellar augite with con¬ 
spicuous grains of feldspar; a mixture of augite, feldspar and 
epidote; a lamellar mineral soft as talc or chlorite; a pale green 
augite, inclosing lamellar augite; augite hyposyenite or perhaps 
diorite; greenish transparent augite in slender prisms; lamellar 
augite in coarse agglomerations, but of a pale green color. 
There were no pebbles of syenite, none of quartzite, none of 
jasper, none of any sedimentary rock. In one instance, I saw 
two or three large grains of quartz imbedded in a large pebble 
*Th8 location is mapped on page 218 of the XVIth Ann. Hep. Minn. 
Geol. Sum., and the facts are given in detail on the succeeding pages. 
