8 NEW YORK STATE MUSEUM 



second iron ore bed; 5 Upper limestone. The exposures of iron 

 ore existing at the time are recorded in detail by both Hall and 

 Vaniixem whose reports, also, are replete with information relat- 

 ing to the character, thickness and other features of the beds. 



The portion of the Clinton belt included in the limits of the 

 Rochester quadrangle, about 13 miFes from east to west, has 

 been mapped by C. A. Hartnagel. The map is on the usual 

 scale of the folio sheets (i mile to the inch) which are in prep- 

 aration for the wdiole State. In the report accompanying the 

 map the five subdivisions of Hall are described under the local 

 names : Sodus shale, Furnaceville iron ore, Wolcott limestone, 

 Williamson shale, Irondequoit limestone. 



The papers by C. H. Smyth jr, contain an accurate and ex- 

 haustive exposition of the origin of the Clinton ores — ■ by far the 

 most satisfactory that has appeared. The evidences Professor 

 Smyth has brought to bear upon the question, from the stand- 

 points of geology and chemistry, must be convincing to any one 

 familiar with the local deposits. For these, at least, the view of 

 secondary replacement which has been advanced by some geolo- 

 gists, may be regarded as completely disproved. A discussion of 

 the subject of origin, with a statement of Professor Smyth's 

 views, is given in a subsequent chapter. 



DISTRIBUTION OF THE CLINTON FORMATION 



The Clinton strata — comprising shales, limestones, sand- 

 stones and interbedded layers of iron ore — are found in a single 

 belt which extends from the "eastern central part of the State 

 to the Niagara river and thence for some distance into the 

 Province of Ontario. The length of the belt, included within 

 the limits of the State, is about 225 miles. 



On the east the strata can be traced into Otsego county, where 

 they thin out to disappearance, though they were' formerly sup- 

 posed to continue southeasterly into Schoharie and Albany 

 counties. From field observations made recently by one of the 

 writers (C. A. Hartnagel) it would appear that they terminate 

 in the town of Cherry Valley, a short distance east of Salt 

 Springville. This is undoubtedly the limit of their deposition 

 in eastern New York. 



West from Otsego county the Clinton belt passes successively 

 through Herkimer, Oneida, Madison, Onondaga, Oswego, 

 Cayuga, Wayne, Monroe, Orleans and Niagara counties ; it 



