THE CfRANITK. 



267 



gradual passage from one to the other perfectly exhibited. This area 

 of the granite with associated diorite is clearly defined, being surrounded 

 by the older limestone, with the relations between the two perfectly dis- 

 tinct. Except at a few points, there could hardly be any confusion be- 

 tween it and the gneisses of doubtful origin, although the granite is itself 

 sometimes prominently gneissoid. 



A more complicated case is presented by a series of granitic rocks ex- 

 tending along the northern boundary of the limestone belt of the town- 

 ships of Diana and Pitcairn. In this instance the granites are quite 

 variable in character, ranging from a rather fine grained to a coarse por- 

 phyritic variety, containing feldspar phenocrysts an inch or more in 

 length. At the same time the color varies, showing white, gray and red. 



The microscope shows much variation in the feldspar of the rocks, as 



plagioclase quite often pre- 



— ' — ' — T — __, 



ponderates over orthoclase. 

 The amount of quartz is also 

 variable, but the dark mineral 

 is quite constantly biotite. 

 These variations suggest that 

 the rocks can hardly belong 

 to a single intrusion ; but for 

 present purposes they may 

 be classed together under the 

 head of granite. 



Only one good contact with 

 limestone has been found 

 along this belt, but this shows 

 abundant evidence of intru- 

 sion, with decided contact 

 metamorphism, resulting in 





7Jm. 





jmn 



Figure 1. — Granite Cutting laminated Gneiss. 

 The drawing is from photograph taken half a mile north 

 of Hiirrisville. 



the formation of a zone composed of 

 pyroxene, scapolite, titanite and garnet. 



The igneous nature of the granite is not, however, dependent upon 

 this single locality for its proof On the contrary, there is a high cliff ex- 

 tending two-thirds across Pitcairn township, which contains most abun- 

 dant evidence of the intrusive nature of the rock. This cliff is made 

 up of finely laminated gneiss, such as occurs interbedded with the lime- 

 stone (and wliich is therefore regarded as a member of the limestone 

 series), cut through and through by granite. At some points the granite 

 sends many tongues and veins into the gneiss, while at others the gneiss 

 is wholly cut out by tlie intrusion. As a result, the cliff at some places 

 consists entirely of gneiss, at others of a mixture of gneiss and granite, 

 and at still others of granite alone (see figure 1). Wherever the granite 



