114 J. D. Dana—Origin of the Rocks of the Cortlandt Series. 
weakened, by finding that among the dikes of igneous rocks 
which intersect the Archzan in various places, some, or none, 
consist of rocks similar to those of Cortlandt. 
Professor Cook, in his Geological Report of 1868, at pag® 
144, has described a labradorite rock, resembling somewhat the 
