436 F. Prime, Jr.—Limonite Deposits of the Great Valley. 
in writing of the ore bed at Kent, Connecticut, speaks of de- 
composed micaceous gneiss (?) called by the workmen “ gre 
fuller’s earth,” and also of “decomposing quartzy mica-slate.” 
We meet with this association of slate or clay and ore in Lehigh 
County, Penn. 
Professor Lesley also speaks of this occurrence in his “ Report 
on the Brown Hematite Deposits of the Nittany Valley, Penn.” 
Here there are apparently three lines of mines, to judge from 
the map accompanying the report. Professor Persifor Frazer, 
Jr., informs me that he found the same association of white 
clay with ore in York County, Penn. 
Professor Lesley + gives a sketch of what he calls “ ore- 
bearing slates” lying between the Potsdam and Calciferous of 
the Cumberland Valley. These are evidently damourite-slates, 
for he proceeds in the article to speak of white clays formed by 
their decomposition. The same association is found in Mary- 
land and Virginia in the valleys forming the Great Valley. 
Professor Lesley* speaks of the occurrence of white clay with 
ore in the same formation at Embreeville, East ‘l'ennessee. It 
also oceurs at Shelbyville. Alabama 
quently what is geologically true of the ore beds at Salisbury 
Amenia, east of the Hudson, is true all the way to Ala- 
ama.” 
rom this constant occurrence of the slate with the ore it is 
evident that the former has exerted an important influence on 
the deposition of the ores; and I think that the presence of 
the slate was necessary to such deposition, in that it formed an 
impervious bed through which the chalybeate waters could not per- 
colate. Whatever may have been the manner in which the ore 
originally existed, it was deposited in and above the slates from 
an aqueous solution. Tater these circumstances, it will be 
* Lesley, “ The Iron Ores of South Mountain in Cumberland Co., Penn.,” in Proc. 
Amer. Phil. Soc., Jan., 1873. + Proc. Amer. Phil. Soe., May, 1872. 
