444 REVIEWS 
The residual clays of Wisconsin are not of much economic importance except in 
the driftless area, where clays resulting from the decomposition of limestone are 
extensively worked for brick manufacture. Glacial clays are important in the north- 
ern part of Wisconsin, and include some of the best and some of the poorest clays of 
the state. Inthe clays of marine origin are included the shales of the Cincinnati and 
Potsdam periods. The Cincinnati series has a thickness of 165 to 240 feet, and con- 
sists of interbedded linestone and shale. The shale varies greatly in composition and 
in hardness. Near the base of the Potsdam in the central part of the state occur 
interbedded layers of very soft plastic blue to brownish clay and coarse sandstone. 
The lacustrine clays are perhaps the most extensive in the state. They are partly 
of interglacial, partly of immediately postglacial age; and in some places the clays 
and interbedded tills have a depth of one hundred feet or more. This thickness is 
not composed entirely of water-sorted material, but includes a considerable thickness 
of bowlder clay with pebbles of igneous rock and limestone. 
River deposits of varying age are common, and furnish much clay for brick 
manufacture. In composition these clays vary with the rocks of the drainage basin in 
which they were formed, the clays of the west central part of the state being the least 
calcareous. 
In Dunn and St. Croix counties extensive deposits of pure white kaolin occur, 
probably derived from the igneous rocks to the northeast and deposited by water prior 
to the first glacial epoch. These clays are of the highest grade, but are now shipped 
exclusively for use in the manufacture of paper. 
Wind-borne clays are of doubtful occurrence, and in the few cases where zolian 
transportation seems probable, the resulting deposits are of no economic importance. 
KUMMEL, H. B. Aeport on the Portland Cement Industry (in New Jersey). 
Ann. Rep. N. J; state!Geologist. for 1o00., Rp..g_-10l,) bigsy 123) Else 
I-2, Igol. 
The first chapter of this report is a discussion of the composition and materials 
of Portland cement in general; the second is devoted to the geologic relations of the 
Cambro-Ordovician rocks of Warren and Sussex counties; and the third contains 
detailed descriptions of the areas of Trenton limestone (‘‘cement rock”’), with notes 
on other limestones and the white marl deposits of New Jersey. 
Overlying the relatively thin Hardiston (Lower Cambrian) quartzite of the Kitta- 
tinny valley is the great magnesian limestone series which has been described as the 
Kittatinny limestone by Weller and Kiimmel, and as the Wallkill limestone by Wolff 
and Brooks. The Kittatinny limestone is usually blue, though often varying to gray 
drab, or even black. It is fine, even-grained, often minutely-crystalline. It usually 
contains 15 to 20 per cent. of magnesium carbonate, and is therefore not available 
for use in the manufacture of Portland cement. 
Resting on the eroded surface of the Kittatinny limestone, and often commencing 
with a basal limestone conglomerate, is the dark blue, fossiliferous Lower Trenton 
limestone. Unlike the Kittatinny, it is never magnesian, but many of its beds are 
shaly. These shaly beds, carrying 65 to 75 per cent. lime carbonate (the remainder 
being silica and alumina), are the “cement rocks” which form the basis of the great 
Portland cement industry of New Jersey and Pennsylvania. The lime carbonate 
needed to carry them up to the proper composition is obtained from other beds (of 
purer limestone) occurring in the Trenton. 
