Wadsworth.] 206 [May 7, 



Sullivan, Hancock County. Here a fine grained argillaceous mica 

 schist was* cut by a diabase dike some forty feet in thickness, in- 

 truded approximately parallel to the bedding. Numerous segre- 

 gated quartz veins cross this diabase and are locally limited to it. 

 The quartz contains calcite, tremolite, chlorite, tetradymite and 

 gold. The geological history appears to be, first, the formation 

 of the sedimentary country rock, secondly, the intrusion of the di- 

 abase, and thirdly, the concentration (mainly from the diabase 

 mass) of the vein materials, including the gold. 1 



MANGANESE. 



At different times in past years, considerable work has been 

 done in New Brunswick on a manganese deposit at a fall of the 

 Tete-a-gouche River, a few miles from Bathurst, on the southern 

 shore of the Bay Chaleur. The country rock is a reddish, fine 

 grained argillite, much fissured and broken. The manganese ore 

 (pyrolusite, wad, etc.) has been infiltrated along the fissures, ap- 

 parently passing from above downwards, and making small irreg- 

 ular gash veins and pockets, the richest portion being in the 

 upper part of the rock. 



Another deposit of manganese has been worked at a locality 

 four or five miles southeast of Truro, Nova Scotia. The country 

 rock is a sandstone and shaly schist, quite indurated, folded and 

 faulted. As before, the manganese ore is found deposited in fis- 

 sures and pockets in the rock, and is infiltrated from above. This 

 deposit, like that at Bathurst, is found on the side of a stream, to 

 which, when cutting its bed, the formation of the deposit is prob- 

 ably due. In such cases as these, the theory of lateral secretion 

 has no bearing, according to the writer's judgment. 



IRON ORES. 



The writer has given sufficient reasons in previous papers 

 why he, in common with some others, can not regard the iron 

 ores of the Marquette District of Lake Superior as coming 

 either under the head of a deposit by lateral secretion or by sedi- 

 mentation ; but holds that they are for the most part of eruptive 

 origin. Those who have opposed this view have in general based 

 their conclusions on theoretical grounds and not on the actual mode 

 iBulI. Mus. Comp. Zool., 1880, vn, 181. 



