16 



GEOIvOGY OF LA SALLK COUNTY. 



but one fossil besides algae was found. It resembles a 

 murchisonia. Fragments of algse are plenty, but not 

 well preserved. Besides these there are vertical holes, 

 perhaps the work of worms, and many markings 

 which have been too little studied to enable one to give 

 an intelligent opinion of their character. These beds 

 will, we believe, well repay the patient, earnest inves- 

 tigator for his time and labor. They seem to speak of 

 shallow seas, of rapid deposits, of sudden changes in 

 the character of the sediments and of a comparatively 

 limited fauna,' and our beds seem to have been deposited 

 on an open shore, exposed to a heavy surf, which 

 accounts for the absence of well preserved fossils, but 

 not for the absence of corals. The waters must have 

 been turbid, too heavily charged with sediment to per- 

 mit those lovers of clear water and wild breakers to 

 flourish in it. 



These beds have for many years furnished water, 

 lime or hydraulic cement, the manufacture having been 

 begun by James Clark at Utica There are how two 

 large manufactories, one at Utica, the other two miles 

 west of the station at the crossing of Pequemsauggin 

 creek. 



The calciferous rocks are overlaid without break • 

 or disturbance by the Chazy or St. Peters sandstone. 

 If the identification be correct, we have here one of the 

 most widely extending formations in the world, for it 

 extends more than half across the continent, and how 

 far north and south is w^holly unknown; certainly some 

 400 miles; in all probability twice that distance. 



The St. Peters sandstone is a vast deposit of 

 silicious matter about 200 feet thick, obscurely strati- 

 fied, varying to some extent in composition from pure 

 silica to a rock nearly half clay, from very coarse to 

 fine grains and in color from white to creamy white 



