MEGASCOPICAL CHARACTERS. 105 



form of this variety is represented in the collection by two specimens 

 (numbers 128, 129), which are quite uniformly granular and without a 

 distinct gneissic structure. The chief constituents, feldspar and augite, 

 are more or less uniformly distributed. 



ELLIPSOIDAL SYENITE-GNEISS. 



In the second phase the rock consists of irregularly ellipsoidal or ovoid 

 masses of feldspar, with more or less quartz, separated by narrow anas- 

 tomosing partitions of green interstitial material, in which there is some- 

 times observed a slight schistosity parallel to the surface of the masses 

 they inclose. This is sometimes apparent also in the tendency of the 

 rock to cleave at the contact between the ovoid lumps and the interstitial 

 material. 



The ellipsoidal masses are usually more or less elongated and arranged 

 uniformly, with the longer axes lying in the same direction. They are 

 of all sizes up to two or three inches in diameter in cross-section, and 

 several inches long. The grain of the feldspathic lumps is coarse in the 

 more spheroidal forms, but becomes finer as the masses become more and 

 more flattened and elongated. They are composed chiefly of feldspar, 

 with a varying amount of quartz and disseminated grains of titanite, 

 augite and apatite. Larger grains of feldspar often appear in the more 

 flattened forms, inclosed in the finer grained mixture. The interstitial 

 material is of finer texture than these ellipsoidal masses, and seems to 

 be composed chiefly of pyroxene, along with finely granular feldspar and 

 some quartz. The interstitial material sometimes has the appearance of 

 two layers of pyroxene separated by a thin light colored lamina feld- 

 spathic in character. In many cases these are seen to represent the 

 wedging out of the ellipsoidal feldspathic masses. Often the thin seam 

 of feldspathic material between two adjoining ellipsoids is found to be 

 directly connected with the small masses of feldspar occupying the angu- 

 lar space between three or more ellipsoids. Sometimes the lumps are 

 flattened to thin lenticular or disk-like forms, which may be bent or 

 folded so as to partially enwrap or inclose adjoining lumps. As these 

 flattened lumps become thin they wrap about the larger ellipsoids, so that 

 when the rock breaks across them the constituents appear to have a con- 

 centric arrangement. In some cases, however, the concentric arrangement 

 could not be traced directly into connection with the flattening of the 

 feldspathic masses. The interstitial bands are composed chiefly of dark 

 green pyroxene, in grains often elongated parallel to the vertical axis, 

 along with more or less finely granular feldspar. The pyroxene grains 

 often lie with their longer axes transverse to the pyroxene band, with 

 their ends .projecting into the feldspathic areas, thus presenting somewhat 



