G02 REPOKT— 1902. 



tliat both are for the most part of Bagshot a<:;e, with the exception only of the 

 deposits that have been rearranged in later times. There is, therefore, good reason 

 for referring to the Bagshot series the beds at Combe Pyne, which are evidently 

 in situ, and which possess so many of the features characteristic of that formation!' 



FRIDAY, SEPTEMBER 12. 

 Tlie following Papers and Report were read : — 



1. On the Viscous Fusion of Rock-furminrj Minerals. By J. Joly, F.Ji.S. 



In a paper read at the Congres Geologique International of 1900, and in 

 a short note communicated to the British Association Meeting at Bradford, I'JOO, 

 experiments on the viscous fusion of some rock-forming minerals are described by 

 the author. It appeared that under the influence of prolonged exposure to high 

 temperatures, rouudiug and other signs of fusion (a breakdown of stability as 

 a solid) could be obtained at much lower temperatures than have hitherto been 

 assigned as the melting-points. This lowering of the melting-point under pro- 

 longed heating (four hours) is more marked generallj' in the case of minerals con- 

 taining a large percentage of silica and most marked in the case of quartz. On 

 this account the order of the melting-points is in general different under conditions 

 of prolonged heating than under conditions of short exposure. 



The former results, as reo;ards melting under conditions of shoi't exposure 

 (lesults required for comparison with those obtained under conditions of long 

 exposure) were not quite satisfactory (as at the time the author pointed out) in 

 so far that the observations were not effected in the same manner as those under 

 conditions of prolonrred exposure. This defect in the observation has now been 

 removed. One-minute exposures have been made of all the minerals previously 

 dealt with on exposures of four hours, and the results confirm the former con- 

 clusions but reveal a decreased difference in the two melting-points ; in other 

 words, the short- exposure melting-points being below previous results, the 

 depression of melting-point upon prolonged exposure is less than formerly deduced. 

 The depression, liowever, increases generally with the silica-content of the mineral, 

 as previously observed. 



2. The Drift MajJ of the Dublin Area. By J. J. H. Teall, F.K.^. 



3. Note on the Volcanic FocTcs of Glencoe, and their Relation to the Granite 

 of Ben Crnachari. By Herbert Kyxaston. 



The ni.ountaiuous district about Glencoe is liuown 1o be occupied by a large 

 area of volcanic rocks. These are described briefly in the ]iiesent communication, 

 together with a small patch in the north-east part of the Blackmount Forest, 

 Some account is also given of the behaviour and order of succession of the rocks, 

 which are t hown to closely resemble the phenomena obsei-ved in the Lower Old 

 Red sandstone volcanic series of Lome. The base of the series is well seen near 

 the western end of Glencoe, where it rests ujion an inclined surface of the older 

 rocks, the slope of the older surface of deposition being to the east. The lower 

 part of the series consists of about 1,600 feet of basic andesites, identical in charac- 

 ter with those of Lome. On the north side of the glen, above Loch Triochatan. 

 conglomerates, sandstones, and shales occur below these andesites, and occasional 

 thin intercalations of shales are found at higher horizons. Resting upon the basic 

 andesites are rhyolitic lavas, followed by agglomerates and breccias, which are 

 capped by about 700 feet of hornblende-andesites. 



' Particulars of the sections are given in the Summary of Progress of the Geo- 

 logical Survey for 1901, pp. 53-50 (1902). 



