302 CEMENT MATERIALS AND INDUSTRY. [bull. 243 
Very few analyses of Tennessee limestone have been publish 
except of the phosphatic limestones of middle Tennessee. This is 
be regretted, since the decision as to which limestones have, an( 
which have not, too great a percentage of magnesia to make the 
available as Portland cement materials is necessarily left to the jud 
ment of the observer. However, with exact correlations and caref 
comparisons with limestones of known composition it is possible t 
attain results sufficiently reliable for the present purpose. 
The bands of limestone in the valley in which the magnesian coiiJ 
stituent is low enough to permit them to be classed as possible factors i 
in the manufacture of Portland cement lie mostly above the Knox if 
dolomite. The}^ are divisible into two series, one occurring in the 
eastern half, the other in the western half, of the valley. ThougB 
probably contemporaneous, the deposits comprised in each of these f 
two series are sufficiently different in lithologic characters and fossil il 
contents to induce the belief that they were laid down in distinct] 
basins or troughs. The beds composing the two series should theremjl 
fore be considered separately and under distinct names. 
CAMBRIAN AND LOWER ORDOVICIAN LIMESTONES OF EAST TENNESSEE*! 
Limestones form but a small part of the lower Cambrian rocks I 
this State. Furthermore, it does not seem probable that any of these 
beds will have the chemical composition now deemed necessary in a 
Portland cement material. Certain layers of the Maryville limestone* 
described and mapped in folios Nos. 12, 16, 25, 27, 33, and 59, pub-' 
lished b}^ the U. S. Geological Survey, probably are more promising! 
for the purpose than any other Cambrian limestone in the State 
Other limestone beds, ranging in thickness from a few feet to nearl; I 
400 feet, have been described under the names of Beaver and Rutledg j 
limestones. Others again are included as calcareous members in the 
Nolichucky and Conasauga shale formations. 
The great bed of limestone known as the Knox dolomite overlie 
these lower Cambrian formations. According to classifications no^ 
in vogue, the lower half of the Knox is referred to the Cambrian sys- 
tem while the upper half is placed in the Ordovician. So far as knownn 
the percentage of magnesia in no part of the 3,500-4,000 feet of lime 
stone comprised in the formation is low enough to permit the rock tct< 
be classed as a possible source of Portland cement material. 
UPPER ORDOVICIAN LIMESTONES OF THE EASTERN PART OF THE 
GREAT VALLEY OF EAST TENNESSEE. 
Lenoir lim,estone. — At the base of the series of Ordovician lime 
stones, shales, and sandstones that overlies the lower Ordovician Kno3 
