19G8-1907.] 501 



water-worn implements seem to prove the existence of man on 

 the banks of the river at a period extremely remote, in view of the 

 report of Mr. Lamplugh to the British Association last year, 

 who thoroughly investigated the nature of the gorge and its zig- 

 zags, that he accepts and confirms the explanation given by Mr. 

 Molyneux, of Buluwayo, who attributed the zig-zags tO' the 

 guidance of the stream-erosion by transverse joints in the basalt 

 plateau through which the gorge has been cut. 



Specimens were examined, and a spirited discussion took 

 place, in which the following members took a prominent part : — 

 Mrs. Hobson, and Messrs. J. M. Dickson, Robert May, Robert 

 Welch, M.R.I.A., John Carson, W. H. Milhgan, and Robert 

 Patterson, M.R.I. A. ; and Mr. Adams having replied, a very 

 pleasant evening was brought to a close. 



THE GEOGONY OF SOME SECONDARY MINERALS. 



The members met in the Museum on Wednesday evening, 

 9th January (Mr. Robert Welch, M.R.I. A., in the chair), and 

 listened with pleasure to^ a lecture by Mr. J. Strachan, of Bally- 

 clare, the subject being " The Geogony of Some Secondary 

 Minerals." In a few preliminary remarks the lecturer dealt 

 with the advantages to the mineralogist of studying minerals in 

 situ, ?,o as tO' gain an insight into^ their modes of origin, by 

 regarding the matrix and the contained minerals occurring in 

 veins and cavities, together as parts, and equally important 

 parts, of one harmonious whole. He next discussed, and briefly 

 described, a number of common minerals which are found in 

 the cracks and cavities of various rocks, both sedimentar)- and 

 volcanic. With the aid of blackboard illustrations and 

 numerous mineral specimens the relationship of secondary 

 minerals to their matrix was clearly demonstrated in certain 

 typical examples. In some cases the origin of the minerals was 

 quite clear to the student of geogenesis, but in others scientific 

 opinion was divided with regard to the source and mode of 

 formation of certain minerals. The subject was then narrowed 

 down to a discussion on the origin and formation of some 



