28 THE JOURNAL OF GEOLOGY. 



Pittsboro, the only rocks seen were of the same general charac- 

 ter. On the farm of Spence Taylor, Esq., in Pittsboro, a bright 

 red porphyry with flow lines is exposed in so altered a condition 

 that it can be easily cut into any form with a knife, though it 

 still preserves all the details of its structure. It looks not unlike 

 the well known pipe-stone, or Catlinite of Minnesota. Three 

 quarters of a mile beyond Pittsboro on the Bynum road there is 

 a considerable exposure of a basic amygdaloid. South of Hack- 

 ney's Cross Roads there are other excellent exposures of the 

 ancient rhyolites with finely developed spherulitic and flow- 

 structures. Numerous specimens were here collected which 

 place the character of these rocks as surface flows beyond a 

 doubt. Another locality in the volcanic belt was visited on 

 Morgan's Run, about two miles south of Chapel Hill. Here are 

 to be seen admirable exposures of volcanic flows and breccias 

 with finer tuff deposits, which have been extensively sheared into 

 slates by dynamic agency. Toward the east and north these 

 rocks pass under the transgression of Newark sandstone. The 

 accompanying sketch-map (Fig. 2) shows the relations of the 

 above mentioned localities in Chatham and Orange counties, 

 N. C. From still another locality at the cross-road near the 

 northern boundary of Chatham county, fifteen miles southwest 

 of Chapel Hill, Professor Holmes informs me specimens of 

 undoubted volcanic rocks have recently been secured ; he has 

 also sent to me within the past month a suite of similar 

 specimens from Pace's Bridge on Haw river, three miles above 

 Bynum. 



In his upper division of the Taconic System in North Caro- 

 lina, Emmons describes numerous beds of "chert or hornstone" 

 intercalated in the slates and sometimes forming isolated bosses, 

 whose origin he is at a loss to account for. He says they are 

 not metamorphic, but does not suggest for them an igneous ori- 

 gin.^ The hypothesis that these rocks may also be of volcanic 

 origin is sustained by Emmons' description of "brecciated con- 

 glomerates" associated with the chert beds, which are composed 



^Geological Report of the Midland Counties, N. C, 1856, pp. 66-68. 



