The Carbonate Ores of the Hudson River. 13 



earths. The more solid ore has to be broken down by blasting ; in 

 the more earthy parts of the deposit it can be picked down and 

 nearly all of the ore be sorted by hand. In mining, pits are sunk 

 and worked open, or drifts are cut from the pit, horizontally into 

 the ore, and much of it is won by underground work. In this dis- 

 trict nearly all of the ore is mined from open pits ; and some of them 

 have reached vertical depths of over 100 feet. The ore is commer- 

 cially known as "rock ore" or " lump ore," that which is sorted by 

 hand, and "wash ore," which is the residue after the earths and sands 

 have been removed by washing. The brown hematite ores of Dutchess 

 and Columbia counties vary considerably in their chemical composi- 

 tion, all containing more or less silica, little or no sulphur, but are 

 rarely low enough in phosphorus to answer for Bessemer pig-iron 

 manufacture. Although there have been many ore localities dis- 

 covered in these counties, twenty-four only have been developed into 

 working mines, deserving of enumeration in this report. 



The earliest iron manufacture in the State was in Columbia county, 

 on Ancram creek, and was probably on these ores. The Salisbury 

 mines in Connecticut, properly a part of this iron-ore district, were 

 opened more than 150 years ago. The causes which have operated 

 in the Highlands, have been effective here also in closing many of the 

 mines, so that, in 1888, there were but nine at work, and four of them 

 were closed during the year. The aggregate output has declined 

 from 144,878 gross tons for the census year, 1879-80, to 43,000 tons 

 in 1888. . 



VI.-THE LIM0NITES OF STATEN ISLAND. 



The group of iron mines on Staten Island is described on a suc- 

 ceeding page, and under the descriptions of iron ores and iron-ore 

 mines. 



VIL-THE CAEBONATE OKES OF THE HUDSON KIVER. 



The mines of spathic iron ore, or carbonate ore, are in the valley 

 of the Hudson river, in Columbia county, south of the city of Hud- 

 son, and in Ulster county near Napanock. The mines south of Hud- 

 son are known as the Burden iron mines ; and, on account of their 

 extent and productiveness, and the comparative insignificance of the 

 Ulster county mines, they may be considered as practically the whole 

 of this group. The range in which the Burden mines are opened is 



