316 The American Geologist. May, 1894 
follows that in investigating - these evidences of prehistoric 
man, the anthropologist may in some cases get some evidence 
as to their age from the kind of rock composing the mortar. 
Two of the mortars collected by the writer are of horn- 
blendic andesite, probably the hornblende- pyroxene- imde- 
site. If these had been reported as occurring under rhyolite, 
a reasonable doubt might arise as to the genuineness of the 
occurrence in light of the succession above indicated. 
A RECONNAISSANCE OF THE ABANDONED 
SHORE LINES OF GREEN BAY. 
By F. B. Taylor, Ft. Wayne, Ind. 
During June and July, 1893, an excursion was made along 
the shores of Green bay in Wisconsin and Michigan with the 
object of locating, if possible, the upper limit of postglacial 
submergence in that region. Dr. F. Savary Pearce of Phila- 
delphia accompanied me during the first half of the season, 
including this trip and several others of which accounts will 
be given separately. I had learned from conversation with 
professor Chamberlin of the existence of abandoned shore 
lines about Green bay, but had no definite knowledge con- 
cerning them. Mr. Leverett had previously explored a part 
of the coast of lake Michigan, but his investigation did not 
extend north of the Illinois state line. He found several ter- 
races, but none of them belong to the age of the great sub- 
mergence here described, as will appear later. 
In this investigation our efforts were confined chiefly to the 
location of the highest shore line. Lower lines were noted 
wherever seen, but no particular effort was made to trace 
them. The principal reason for this is that the highest line 
marks the maximum of submergence and may, therefore, be 
more safely extended than any lower line by inference from 
place to place where not continuously traced. For this reason 
it is also a more reliable index of deformation. Wherever 
the full extent of the shore line is known it constitutes an 
absolute criterion for the determination of the amount of 
change of land attitude. No lower shore line can be relied 
upon for such an inference unless it is traced with absolute 
