Geological Society. 4 6" 5 



composite in character, consisting of minute examples of the 

 common type enclosed in larger arborescent growths (' porous- 

 sphenilites ') of felspar microlites, with silica, originally in the 

 form of opal and tridymite, bnt now converted into quartz, lying 

 between them. All the interesting forms of spherulitic growth 

 which have been so well described by Mr. Iddings from the Obsi- 

 dian Cliff in the Yellowstone Park, and by Mr. Whitman Cross from 

 the Silver Cliff, Colorado, are most admirably illustrated in these 

 inclusions of the Cuilin Hills. It is interesting to note that the 

 nuclei of some of these large spherulites consist of fragments of the 

 micropegmatitic granite which have escaped fusion. Among.the new 

 minerals developed in these inclusions, by the action on them of 

 the enveloping magma, are pyrites and fayalite (the iron-olivine). 



The phenomena now described are of interest as setting at rest 

 all doubts as to the order of eruption of the several igneous masses 

 of the Western Isles of Scotland. That the gabbros are younger 

 than the granites was maintained by Macculloch in 1819, by J. D. 

 Forbes in 1846, by Zirkel in 1871, and by the author in 1874. In 

 1888, however, Sir A. Geikie asserted that these conclusions were 

 erroneous ; he insisted that the granites were erupted after the 

 gabbros and basalts, and that they are, indeed, later than all the 

 volcanic rocks of the district except a few basic dykes which are 

 seen to traverse them. The occurrence of the remarkable inclusions 

 of granite within the gabbro now removes all possibility of doubt on 

 the subject, and proves conclusively that the granite was not only 

 erupted but had consolidated in its present foim before the outburst 

 through it of the gabbro. 



2. " Anthracite and Bituminous Coal-beds. An Attempt to 

 throw some light upon the manner in which Anthracite was formed ; 

 or Contributions towards the Controversy regarding the Formation 

 of Anthracite." By W. S. Gresley, Esq., F.G.S. 



The author does not seek to advance any new theory in this 

 communication, nor to proclaim new facts of any importance, but to 

 put old facts in something of a new light, in order to aid the inves- 

 tigations of others. His main object is to establish two facts, viz.: — 

 that the associated strata of anthracite-beds are more arenaceous 

 than those containing so-called bituminous coal-beds, and that the 

 prevailing colours of the sandstones, grits, etc., of anthracite regions 

 are greyer and darker than those of regions of bituminous coal. To 

 these facts may perhaps be added a third, that the more anthracitic 

 the coal-beds, and the more siliceous the enclosing strata, the harder 

 and tougher these associated strata are. 



While recognizing that the rocks of many anthracite regions have 

 undergone great disturbance, he cites other areas where coal-basins 

 have been much folded, without any corresponding production of 

 anthracite in considerable quantity. 



The modes of occurrence of anthracite arc illustrated by many 

 instances observed bv the author in the Old and New Worlds. 



