448 Macfarlane on the Acton Copper Mine. 



a fine-grained greenstone, which sometimes forms very con- 

 siderable and irregular masses, sometimes intersects the limestone 

 strata, and often presents a peculiar banded structure, resembling 

 more that produced by igneous flow, than that due to deposi- 

 tion from water. This greenstone, although intruded most fre- 

 quently between the underlying shale and the cupriferous lime- 

 stone, is sometimes observed occurring between the latter and the 

 hanging shale. This hanging shale, of a black color, which 

 overlies the cupriferous limestone, is also often impregnated 

 with copper pyrites, and has a very considerable thickness. It 

 has not yet been ascertained what rock overlies the hanging shale 

 in the immediate neighborhood of the mine, but from observa- 

 tions elsewhere, it appears to be followed by lighter colored shales, 

 containing small interstratified quartz veins. Upon these shales is 

 superposed a finely and evenly foliated clay-slate, with transversal 

 cleavage. At greater distances from the mine there is found a 

 considerable development of clay-slates and sandstones ; some of 

 the latter posses-^^ing the characters of the greywacke sandstone 

 of German geologists. The whole of these rocks are apparently 

 destitute of organic remains. According to Sir William E. Logan, 

 they constitute a part of the Quebec group, of the Lower Silurian 

 series Referred to the systems of continental geologists, they 

 ■^ould appear to occupy a place between the primitive slate forma- 

 tion and the Silurian, in a forraation corresponding to Barrande'a 

 Azoic formation in Bohemia, or to the Cambrian system, as 

 this is understood to be constituted by Cotta ; viz., of less crystal- 

 line clay-slates and silicious slate, of non-fossiliferous greywacke 

 sandstone and conglomerate.* 



Having thus referred to the geological character and age of the 

 rocks in the neighborhood of the mine, I proceed to describe the 

 various workings above named. Flowers's pit, the most north-east- 

 erly of the open workings, has a triangular shape, an average width 

 of forty-five feet, and had in September, 1861, a depth of twenty 

 feet. The bottom of the excavation consisted, on the south-easterly 

 side, of shale, while the outcrop of the cupriferous limestone, hav- 

 ing a thickness of four feet, ran along the north-west side. The 

 original thickness of forty-five feet of limestone, had thus, on 

 account of a fold in the underlying shale, decreased to four feet, 

 as shown in the following section at No. 4 shaft. 

 'The excavation of the limestone at a was continued, (the point 



j_*Cotta: Die Flo tz Form^tionen^p. 204. 



