46 Reports & Proceedings — Geologists Association. 



with the lamprophyres, the series ranging from modijS.ed biotite- 

 porphyrites to modified pilitic lamprophyres. 



The later intrusions are typically free from the large orthoclase- 

 felspars, though quartz-grains may occur even in the basic members. 

 Associated centrally with the earlier set they are distributed over a 

 much wider area, overlapping the former in every direction. They 

 are the result of further differentiation, and are assigned to a later 

 period when igneous activity was renewed on a more or less regional 

 scale. The rocks include acid felsites and spessartites. 



The rocks of the earlier set agree in general direction with the 

 north-north-west fractures transverse to the strike of the country 

 rock, while the later intrusions trend generally east of north. 



V. — Geologists' Association. 



Decemher 1, 1917. — George Barrow, F.G.S., President, in the Chair. 



The following lecture was delivered: "The Gold Coast." By 

 Albert Ernest Kitson, P.G.S., Director of the Geological Survey of 

 the Gold Coast. 



The features to be considered, after a general description of the 

 geography and tectonics of the colony, are: the Arch sean gneisses, 

 schists, amphibolites, etc., principally of the Eastern Provinces; the 

 folded and zonally contorted pre-Cambrian, or early Palaeozoic, 

 altered sediments (conglomerates, quartzites, etc.), with interbedded 

 volcanic rocks (rhyolite, andesite), flanking the former group and 

 extending westward across the colony; deposits of gold and 

 manganese. 



Intrusions (into both groups) of granites, syenites, diorites, 

 gabbros, etc. ; dolerite volcanic necks ; gold, tin, ilmenite, and 

 molybdenite associated with these rocks. 



The slightly inclined sedimentary rocks of the coast (with 

 Devonian fossils) and of the greater part of Ashanti and the IS'orthern 

 Provinces with bauxites, oil-shales, and clays ; the Tertiary deposits 

 of Apollonia with bitumen and oil, the " laterites " and associated 

 iron-ores. Eluviatile, estuarine, and seolian deposits. 



The evidence of aboriginal occupation, consisting of stone-imple- 

 ment factories, camps, and crude forts, was also discussed. 



COE.E.ElSIE'OlSriDEIsrCE!. 



WOEM-BOEINGS IN EOCKS. 

 Sm^ — ]3r. Bather's interesting communication on " Salt- weathering 

 and supposed Worm-borings in Australia " (Geol. Mag., November, 

 1917) induces me to direct attention to a paper read by the late 

 Duke of Argyll before the lioyal Society of Edinburgh in January, 

 1889. In this he described similar tubes occurring in some of the 

 quartzites of Sutherlandshire, and whicli he and the late Mr. Etheridge 

 attributed to the burrowing of annelids. Some of these tubes were 

 horizontal, having been drawn out of the vertical by movements due 

 to shearing or slipping of the beds or laminae of the deposit. 



