244 The American Geologist. October, 1904. 
the quartzvte that on reconcentration by white quartz ir pre- 
sents the composition and structure of Reibungs breccia. In 
general this quartzyte is cemented by "interstitial" quartz, and 
small amounts of iron oxide, chlorite and sericite. 
The conglomerate underlying the quartz}i;e is essentially 
composed, even where it lies on or near the granite, of rolled 
and angular pieces of the rhyolyte, i. e., it is a quartz porphyry 
conglomerate indistinguishable from the red conglomerates of 
the Keweenawan. It contains, however, a little black slate, 
some pebbles of greenstone and some of ferruginous chert 
rocks, in that respect resembling the conglomerate underlying 
the New Ulm quartzyte of JNIinnesota. 
The so-called "intra-formational" conglomerate beds situ- 
ated on or in the qurtzyte, should not perhaps receive that des- 
ignation since after careful examination microscopically by 
Dr. Weidman they do not contain any pebbles of the underly- 
ing Baraboo quartzyte, but consist of "pebbles of chert contain- 
ing considerable iron oxide and also a few pebbles of slate, but 
mainly of pebbles of vein quartz or of quartzyte like the Rib 
Hill quartzyte in north central Wisconsin." Such coarse frag- 
mental material, entirely foreign to the quartzyte vmderlying 
and overlying, indicates the sudden occurrence of powerful 
transporting currents in the ocean which ordinarily deposited 
the fine-grained quartzyte. What may have been the cause of 
such powerful currents the author does not enquire, but it has 
a suggestive relation to the Keweenawan. What may have 
been the source of the "ferruginous chert," which we suppose 
is the same rock as that term expresses in other publications 
by the Wisconsin geologists, the author does not inquire, but 
it has an important bearing on the age of the quartzvte in 
which these pebbles exist. 
Dr. Weidman has made a very important contribution to 
geology in establishing the structural relations of the quartz- 
yte to the rhyolyte and the granite of the district. \'erv differ- 
ent conceptions of these relations had been published bv dif- 
ferent geologists of the Wisconsin survey. Dr. Weidman 
shows by a mass of detailed field observations that the quartz- 
yte is younger instead of older than the quartz porphvrv. that 
the structure of the region, instead of being monoclinal as 
thought by Irving and by Chamberlin, or anticlinal as conceiv- 
