GEOLOGY OF THE MERRIMACK DISTRICT. 513 



with the slope of the hill. This jointing enables the quarrymen to 

 remove immense slabs that are only a few inches in thickness. In parts 

 of the quarry, however, the joints are not so frequent, and large blocks 

 for building or other purposes can be obtained. At the quarry on the 

 eastern slope of the hill the joints are not so frequent, and, among the 

 other desirable qualities of the rock obtained here, it is susceptible of a 

 high polish. 



With this light granite there is a dark rock that is extensively quarried. 

 This rock we suppose to be a gneiss, and a more specific description than 

 that already given will naturally come in the chapter on building-stones. 



A section through the hill south of the station shows the dark gneiss 

 on the south-east and the light gray granite at the quarries. But, a few 

 rods north-west of the principal quarry worked by Mr. D. M. Reed, he 

 has made an opening to obtain the dark gneiss ; and here it is that we not 

 only find the light gray granite in contact with the dark gneiss, but many 

 veins of the granite penetrating the gneiss. The light gray granite is 

 certainly intrusive here. 



On the railroad, in a cut about ninety rods above the Richmond road, 

 we have an exposure of the granite and the schist. On the right hand, 

 as we enter the cut from the south-east, we find the schist nearly vertical, 

 and extending to the bottom of the cut. But a few steps, and the granite 

 suddenly appears, three or four feet above the rails, and it gradually 

 rises until it reaches the surface of the ground. Except at the top of the 

 cut the strata of the schist stand nearly vertical on the granite. After 

 extending a short distance along the surface the granite is again capped 

 by the schist, and soon disappears altogether. 



Starting again from the south-east, on the left opposite the schist, the 

 strike of which should carry it across the cut, we have nothing but gran- 

 ite, and we find the schist again only as we pass out of the rock cutting. 

 Metamorphism may explain what we see here ; but that the granite is 

 intrusive is more probable. 



Another interesting feature in the rocks here is, that below the Rich- 

 mond road the porphyritic granite or gneiss is very near the light grey 

 fine-grained granite, the intervening space being covered with drift. 

 The porphyritic rock elsewhere seems to be stratified ; but we have here, 

 on the road from the station to the village, immense boulders of the 

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