326 ME, ALFEED HAEXEE ON THE [May 1 896, 



the circumstances are different. In one example are seen ring-like 

 aggregates, about y 1 ^ inch in diameter, of hornblende-crystals, sur- 

 rounding areas of clear quartz (6705, PI. XIII. fig. 6). Quartz is 

 frequently seen moulded upon hornblende-crystals, and, in several 

 slides, penetrated by actinolitic needles (PI. XIII. fig. 5). Such 

 patches of quartz are quite different from the quasi-porphyritic grains 

 common in the granophyres, and they seem to be of late formation — 

 not necessarily secondary in the usual sense. They probably occupy 

 what have once been vacant spaces formed in connexion with the 

 destruction of xenoliths, and are quite distinct from druses. The 

 latter are also found here just as in the normal granophyres, and 

 are commonly filled by calcite and quartz (6707, PI. XIV. fig. 8). 

 In places it can be seen that the calcite-crystals project into the 

 quartz, which again indicates that some of the latter mineral belongs 

 to a very late stage in the history of the rock. 



In addition to the relics of gabbro in these granophyres there are 

 occasional traces of inclusions of other rocks. In particular there are 

 granular aggregates consisting largely of hornblende and magnetite 

 and presenting angular outlines to the surrounding matrix (6709, 

 PI. XIV. fig. 10). These probably represent xenoliths of basalt in an 

 advanced stage of dissolution. At junctions of basalt and granophyre 

 in other parts of Skye, as well as in Rum, Mull, and Ardnamurchan, 

 detached fragments of basalt in the granophyre can be traced down 

 to quite similar aggregates. In some cases the ferro-magnesian 

 mineral produced is augite ; in other cases, as here, it is hornblende. 

 The greater part of the rocks now described contain no trace of 

 foreign fragments other than those of gabbro. 



There are, however, certain fine-textured portions of these 

 granophyre-masses to which allusion has not yet been made, and 

 the xenoliths in these are of a different character. The rocks occur 

 on the margin of an intrusion or as a ]imb extending from the 

 main body, and it is not easy to decide whether these and the 

 more usual coarse type represent parts of a single intrusion. The 

 granophyric structure is absent or scarcely developed in these fine- 

 grained rocks, and one example shows strong fluxion (PI. XIV. 

 fig. 12). The enclosed fragments are very distinctly seen in hand- 

 specimens, are subangular to rounded in shape, and are chiefly of dark 

 compact lava, usually not more than J : inch in diameter. One slide 

 shows recognizable pieces of basalt, partly vesicular, of microlitic 

 andesite, and of a quartzose grit (6701, PI. XIV. fig. 11). Another 

 shows only basalts, one with porphyritic felspars (6702). Gabbro 

 has not been identified, and the fragments noticed are all such as 

 might be obtained from the agglomerate through which the intrusions 

 have broken. They are in no case very highly altered, and, though 

 their rounded form points to a certain amount of absorption by the 

 magma, the latter has clearly not been very considerably enriched in 

 basic constituents. In all these points these rocks contrast with the 

 coarser granophyres described above. 



The fine-textured rocks, with their evidence of comparatively 

 rapid chilling, presumably represent the earliest irruptions of the 

 acid magma. The marked difference between them and the coarser 



