of Portland, Dodge county, Wisconsin. 288 
S.W. corner of Dodge county, at least thirty-five miles from 
the Sauk county metamorphic rocks, and fully eighty-five miles 
from the nearest puint of the main Azoic body of the northern 
portion of the State. 
_ I have ascertained, I think, all that has heretofore been pub- 
lished about this locality. The first public announcement 
seems to have been made by Dr. I. A. Lapham in a lecture at 
of Owen’s Report on Wisconsin, Iowa and Minnesota (1852), 
and from which I take the following: “The late Mr. J. S. 
the ridges adjoining the Baraboo valley, on the north and south, 
Baraboo (Sauk) quartzites are ¢ anged “ Lower” or Potsdam 
sandstone, whilst the Portland rocks in like manner result from 
the “ Upper” or St. Peter’s sandstone. In Mr. Hall’s Reports, 
k.# 
much 
farther south than any of the similar isolated masses, we fin 
now in the immediate vicinity not merely the sandstone, or lower 
Tepresentative of the Potsdam period, but also, and Rewer the 
wer Magnesian limestone or upper representative 0: that 
period. We find too, within a very short distance, the St. Peter's 
or “ Upper” sandstone, and the Blue and Buff limestones, all of 
the Trenton period. In this case, then, the occurrence is even 
more strikingly peculiar than in the Sauk county region. Here 
we find a very much smaller area covered by the metamorphic 
rocks ; these rocks are much further from the main Azoic mass, 
and the series of surrounding and entirely unaltered and un- 
disturbed strata is much fuller. The meats: ride map, en- 
larged from Dr. Lapham’s Geological Map of Wisconsin, serves 
logical Survey of isconsin, for 1861, that he gives more proof uronian 
or Azoic age of Sauk quartzi T supposed bin 5 ‘eget tes Melicle ninated 
to above. He ma; ore proof in reserve for the final Ww) 
reached only one volume before the survey was stopped. 
petitions. di ate the i eae ek wo 
‘olds, instead of having a uni, 
ideas then entertained wien regard to these rocks must have been erroneous. 
