Limonites of Dutchess and Columbia Counties. 53 



forms with the Sylvan Lake Mine a connected opening about a quarter 

 of a mile long, and has an average breadth of 200 feet. The vertical 

 depth is about 90 feet. The ore is covered by drift earth. In places 

 it has been found within a few feet of the surface ; at other points as 

 much as 30 feet of glacial drift, boulder clay and ochreous earths are 

 found over the ore. No rock in place has been encountered in the 

 excavations ; and the nearest outcrop is that of a light blue limestone 

 20 rods south-east of the mine. The same formation appears to the 

 north, near the lake. Both blue and yellow "ochres" occur with 

 the ore, in masses of irregular shapes and of varying extent. About 

 ten per cent, of the ore is lump or " rock ;" the rest is wash material. 

 The former is picked out in the mine. The "ochres" also are separ- 

 ated as far as possible, in the digging. " Bombs," stalactitic, and 

 compact masses occur. Thus far no carbonate or " white horse" has 

 been found. There are two slopes on the north side of the pit, 400 

 and 384 feet long, respectively. The ore is reported to average 47 

 per cent, of metallic iron, eight per cent, of silica, with traces of man- 

 ganese and no sulphur; phosphorus, .07 per cent. It is a non- 

 Bessemer ore. The mining plant consists of two hoisting engines : 

 one 13x24" and one (Corliss) 14x30"; two 75-horse-power boil- 

 ers ; two steam-pumps ; two Cornish, plunger pumps, and two ore- 

 washers. A track runs from the washer to the Clove Branch railway. 

 The mine makes a large volume of water, draining the adjacent 

 Sylvan Lake pit, and the pit water serves for washing the ore. 



The market for the ore is at Troy and Poughkeepsie, and in the 

 Lehigh region of Eastern Pennsylvania. A. E. Tower & Bro., of 

 Poughkeepsie, are the lessees. 



The Sylvan Lake Mine has been idle for six or seven years. 

 It is owned by the proprietors of the Clove Iron Works. The geo- 

 logical relations of the ore are similar to those of the Fishkill mine, 

 excepting the greater thickness of the overlying drift and ochreous 

 earth. At present the pit is drained through Tower's mine. In 

 these Sylvan Lake mines the exploitation is done by driving hori- 

 zontal drifts into the ore, in advance of the mining, and its extent 

 ahead is ascertained. In mining, the overlying earth and ore are 

 thrown down in large sections, by great blasts, and then roughly 

 sorted into lump or rock ore, wash ore and waste dirt and stone. 

 The volume of water is large — from the large drainage surface of pit 

 area, as well as underground water. The bottom of the mine is 

 considerably lower than the level of the lake. 



