146 Scientific Intelligence. 



across it, tliirty-fivo or forty feet, without meeting any interruption. In- 

 deed, the "whole of the hill consists of alternating beds of quartz, talcoso 

 and specular schists. The greatest thickness of the latter is between the 

 itacolumite and talcose slate. The strike of these beds is N. 41^ E., the 

 dip 64^ S., 49"* K, but owing to folds of the rocks, some quartz beds 

 strike N. 5° E., and some of the talcose slate N, ll"" E., both being verti- 

 cal in dip. The interrupted extension of the beds of the specular slate 

 northwest and southeast at this point is about half a mile, though in its 

 northeastern prolongation it gradually becomes narrower, until east of the 

 place of A. Harding, Esq., it finally gives out. 



On the Dolittle mountains we find this remarkable rock not only most 

 perfectly developed as regards extent, but also most strongly marked in 

 its peculiar petrographic charactei-s. Here it presents so great a similar- 

 ity Avith some micaceous schists, that, at first sight, few would suppose it 

 to be anything else. In color it is steel-grey, but its crimson streak, when 

 -Scratched, distinguishes it from mica-slate, to which it possesses a resem- 

 blance in the laminated or scaly nature of the individual parts of the 

 iron glance. Sometimes, especially farther north, this feature disappears 

 to a considerable extent, and the rock becomes less schistose and granular, 

 owing to the shape of the minute crystals of the iron ore- In these cases 

 talc generally enters more conspicuously into the composition of the 

 rock, and, owing to the presence of a small admixture of magnetite, it 

 becomes slightly magnetic. As an ore this rock is greatly valued at the 

 furnaces, though not used to any extent at the bloomcries. 



Where atmospheric action has been able to affect the rock, the specu- 

 lar iron (anhydrous peroxyd) is converted into earthy hematite (hydrated 

 peroxyd). This generally forms as a crust and the mass contains harder 

 nuclei. 



The magnetic iron beds of this region seem to be in part synonymous 

 with the itahiriie of Eschweije. We have indeed the true itabirite, that is 

 an itacolumite in which the talc is replaced by magnetic iron, although 



generally in South Carolina the quartz is present in less quantity, and the 

 accompanying talc greatly increased in amount to that which, according 

 to d^cription, seems to be the case at the Peak of Itabira, the Sicrra-da- 

 Piedada and other Brazilian localities. With us the rock essentially con- 

 sists of talc (or chlorite) and crystals of magnetite, the former being the 

 matrix of the latter, while talcose strata less admixed with magnetic iron, 

 are intercalated between the others. These do not affect the needle, 

 while the former are highly polaric. Wherever I have examined beds of 

 this rock, as for instance at the Lee and Parker bank and the ore beds of 

 the Swedish Iron Manufacturing Company in the corner of Union (both 

 of which are outcrops of the same bed), dikes of melaphyre or diorite 

 appeared in the immediate vicinity ; so that it is not impossible, that the 

 magnetite may have resulted from a partial reduction of the peroxyd of 

 iron of the specular schist to a protoxyd. 



This rock also occurs at the junction of the itacolumite and talcose 

 slate, and, therefore, ffives additional reason for regarding it as a continua- 

 tion of the specular beds, although separated from it superficially by the 

 itacolumite. At the I^e and Parker ore bank it is immediately underlaid 

 by a barytic vein, the width ot which has not yet been determined* The 



