172 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



have all the lithological characters of the Laurentian as dis- 

 played in the Lauren tides, the Adirondacks, and in the South 

 Mountain between the Hudson and Schuylkill rivers. They 

 consist of gneisses frequently granitoid, often hornblendic, 

 but scarcely micaceous, which are penetrated in the vicinity 

 of Georgetown, Colorado, by well-marked granitic masses 

 probably exotic. Similar gneissic rocks are found in Glen 

 Eyrie and the Ute Pass, in Colorado, where large masses are 

 often highly granitic in aspect, with rarely interbedded gneis- 

 sic layers. These rocks, which the writer regards, with Mar- 

 vine, as indigenous, had already been by the latter observer 

 compared with the Laurentian. The red granitoid rocks at 

 and near Sherman are also by Hunt regarded as Laurentian 

 gneisses. Labradorite rocks having the characters of the 

 Norian series, and associated, like that series in the east, 

 with large masses of titanoferrite, are known in Wyoming 

 Territory. 



The gneissic rocks of the Wahsatch range, as seen in the 

 Devil's Gate on the Weber River, are also Laurentian, to 

 which are referred the similar stratified rocks found in the 

 same range farther south, in the upper part of the Little Cot- 

 tonwood canon. Here, among loose blocks of the gneiss, 

 are found occasional masses of coarsely crystalline limestone 

 with mica, and varieties of pyroxenic rocks characteristic of 

 the Laurentian. In the lower part of the same canon are, 

 however, well-marked eruptive granites. The crystalline 

 schists met with at the western base of the Sierras in Ama- 

 dor, Placer, and Nevada counties, in California, are described 

 as having all the characters of the Huronian series as seen in 

 Eastern North America and in the Alps. To this horizon, also, 

 Hunt refers the similar crystalline rocks of the Coast range 

 of California, as seen near San Francisco and near San Jose. 

 The auriferous quartz veins in the counties above named are 

 found traversing alike the Huronian schists and the granites 

 of the region, which are, probably, newer than the schists. 



EOZOIC ROCKS OF THE BLUE RIDGE. 

 Referring to the observations on the geology of North Car- 

 olina in the Record for 1875 (page c), we may notice that 

 Hunt has given a preliminary account of his late observa- 

 tions in a section across the Blue Ridge through Mitchell 



