T. B. Brooks—Rocks observed in the Huronian Series. 203 
26 
but not abundant. Was not observed in the Penokie series. 
8. CALCAREOUS Rocks.—CARBONATES AND SULPHATES. 
1. Unerystalline Limestones. Not observed. 
2. Crystalline Limestone. 
Tolerably abundant, especially in the Menominee Region. 
Usually dolomitic. In the Marquette Region it is always 
associated with quartzyte, and contains interstratified beds of 
clay slate (novaculyte) with oblique cleavage. 
(L.) Granular Limestone—rare. Ferruginous—97; very rare, 
probably a vein. Brown, micaceous—144; observed at one 
point in the Marquette Region. 
_(2.) Dolomyte and Dolomitic Limestone.*—Most if not all the 
limestones in beds contain more or less carbonate of magnesia. 
crystals of tremolite, and, according to Dr. Wichmann, o 
4. IangEous oR ErvuprivE Rocks. 
: (Including those metamorphic rocks which in a plastic state 
ave been forced into adjacent cracks, thus taking the form of 
eruptive rocks), 
1. Feldspathic Series. 
ct) Granite dykes or veins have been observed only in the 
seh and Upper Huronian of the Menominee Region. Red 
nous granite in iron-ore at two points—96. Gray granite 
Dr. Credner erroneously assigns certain dolomytes and conglomerates to the 
1869, Zeitschrift dee dncbahen: geologischen Gesellschaft, xxi Band 
aes 516, bles, so abundant in the Laurentian of Eastern Canada have 
48 yet I believe been observed in that system as developed south of the lake. 
