234 Reports & Proceedings — Geological Society of London. 



Eacliael "Workman McRobert, B.Sc. (Communicated by E. B. Bailev, 

 B.A., F.G.S.) 



This communication deals with the igneous rocks which fall within 

 au area about 7 miles square, included in Sheet 25 of the Geological 

 Survey map of Scotland, and which lie in the neighbourhood of 

 Galashiels, Selkirk, and Melrose. Tlie age usually assigned to the 

 igneous intrusions is a late period in the history of the ' plateau - 

 eruptions ' of Calciferous Sandstone times, and thus corresponds 

 to those of the trachytic lavas and intrusions of the Campsie and 

 Renfrewshire Hills. 



The relation of the igneous rocks to the Old E,ed Sandstone is 

 discussed, and new localities are cited where a protective covering 

 of igneous rocks has resulted in the preservation of small outliers 

 of Old Red Sandstone, far removed from the main outcrop of the 

 formation. 



The main portion of the paper deals with the petrology of the 

 igneous rocks, which occur as laccolites and sills, as dykes having for 

 the most part a north-easterly direction, and in volcanic necks. 



The chief rock-types present in the area described may be 

 summarized as follows : Porphyritic and non-porphyritic sanidine- 

 trachytes, quartz - trachytes, riebeckite - f elsites, quartz - porphyries, 

 basalts, and volcanic agglomerates. The sanidine-trachytes present 

 a number of varieties, characterized either by the presence of fresh 

 riebeckite, by the presence of segirine-augite and olivine, or by the 

 absence of any fresh ferromagnesian minerals. The more acid types 

 described maybe regarded as standing midway between the phonolites 

 and trachytes of the same age which occur south-east of Hawick and 

 those of East Lothian. 



In addition to the description of the various rock-types which occur 

 as isolated sills and dykes, the geology of the Eildon Hills is discussed 

 in some detail, and a petrographical account is given of the rocks in 

 that region. The author has traced as far as possible the distribution 

 of the various rock-types, and has come to the conclusion that the 

 Eildon Hills form the eastern section of a composite, complex laccolite. 

 A basaltic neck has been met with in the Eildon Hill complex, and 

 appears to cut through the more acid intrusions which form the main 

 portion of the Eildon Hills. The record of riebeckite in the rocks of 

 this region has been considerably extended. 



The salient features of the suite of rocks described are the high 

 content of alkalies and the presence of soda-bearing minerals such 

 as I'iebeckite, segirine-augite, primary albite, and soda-orthoclase. 

 j^epheline, however, though its presence might be expected in some 

 instances, was found to be absent from most of the rocks. 



2. " Correlation of Dinantian and Avonian." By Arthur Vaughan, 

 M.A., D.Sc, F.G.S. 



The present paper records the results of applying the time-scale 

 deduced from the South-Western Province to the Belgian sequence, 

 and shows that the faiinal succession is practically the same in both 

 provinces. Even the specialized and locally exaggerated facies which 

 form so striking a feature of the Belgian Province (such as the ' petit 



