166 T. H. Holland — Slab of Chinese Agglomerate Lava. [No. 3, 



Lumps of andesitic rocks are common as inclusions in the matrix, 

 which in places shows damascened and eutaxitic structures. 



The specific gravity of the rock is 2"35. Thin splinters fuse before 

 the blowpipe to a white vesicular glass. 



Comparison with Chinese rocks : — The peculiar structures presented 

 by this rock are of especial interest from the way in which they can be 

 parallelled amongst the Chinese eurites and rhyolifces. The damascened 

 structure and the included fragments of a similar andesitic rock I have 

 previously described in the Korean acid lavas.* 



Amongst the rocks which I have collected in China, there is a speci- 

 men of eurite from the Victoria Peak, Hong Kong, in which the porphyr- 

 itic crystals of quartz are cracked in the same peculiar manner. The 

 felspars, also, in this rock are in part plagioclastic, and irregular patches 

 of small biotite bundles resemble in shape the ferruginous masses occur- 

 ring in the slab. But although the Hong Kong rock shows a very dis- 

 tinct flow structure, the groundmass is composed wholly of micro- 

 granulitic material, and there is a notable absence of the andesitic foreign 

 inclusions. Whilst, then, the porphyritic constituents of the slab 

 a"ree with those of this rock, the groundmass shows that the conditions 

 of consolidation were different ; but although the circumstances of soli- 

 difi.cati.on were not the same thei*e seems little doubt that the slab in St. 

 John's Churchyard belongs to the same geological mass as the Hong Kong 

 eurite, and both these are members of the acid series of igneous rocks — 

 granites, granitites +, eurites and rhyolites — which can be traced from 

 the Island of Hainan, north-east through Hong Kong to Foochow, and 

 are repeated in a parallel band which reaches the sea-coast at Chusan, 

 are repeated in the Korea, and possibly represented again by the central 

 granitic axis of Kamtschatka. These rocks probably belong to one petro- 

 graphical province and are the relics of a great chain of eruptions which 

 took place in East Asia during middle carboniferous times. The granites 

 and eurites are found intruding into the limestones which occur below 

 the coal-bearing series ; whilst fragments of these rocks are the principal 

 constituents of the conglomerates which lie at the base of the coal- 

 measures. The out-crop of these rocks is approximately parallel to the 

 general strike of the stratified series, following the directions of the 

 principal mountain ranges, which in East China Pumpelly has described 



* Quart. Journ. Geol. Soc, Vol. XLVII. (1891), pp. 176-178. 



f The prevalence of granitite and the occurrence of its representatives amongst 

 the hetnicrystalline and felsitic rocks are striking features in these Chinese rocks, 

 and I regard them as a later stage in the eruptions which first gave rise to diorites 

 and andesites — rocks which I have frequently found associated with and included 

 in the later acid eruptions of China. 



