Mode of Occurrence of Diamonds in South Africa. 311 



In the Upper Punjab the junction follows a curved line, running 

 nearly east and west to the north of Rawul Pindee ; then de- 

 scribing an angle which closely follows the great bend of the Jhilam 

 river near Mozufferabad, it runs more or less in a south-easterly 

 direction through Kashmere towards Simla. This junction line is 

 inseparably connected with the causation of the great mountain- 

 chains ; it shows a parallelism to the axes of the outer ranges, and 

 is chiefly due to intensity of disturbance, the result of lateral 

 pressure. 



The author also refers to the difference existing between the 

 geology of the outer Himalayan region and that of the Salt Range, 

 as being similar to that which obtains between the Alpine and 

 extra-Alpine characters of European rock-groups, and suggests that 

 the recurrence of such similar features at such distances may indi- 

 cate a connexion between the former conditions o"f deposition and 

 the early history of the great chains themselves. 



2. " On the mode of occurrence of Diamonds in South Africa." 

 By E. J. Dunn, Esq. Communicated by Prof. Ramsay, E.R.S., 

 V.P.G.S. 



In this paper the author stated that the diamonds of South Africa 

 occur in peculiar circular areas, which he regards as " pipes," which 

 formerly constituted the connexion between molten matter below 

 and surf ace volcanoes. The surrounding country consists of horizontal 

 shales, through which these pipes ascend nearly vertically, bending 

 iipivards the edges of the shales at the contact. The rock occupying 

 these pipes was regarded by the author as probably Gabbro, al- 

 though in a very altered condition. Intercalated between the shale- 

 beds there are sheets of dolerite &c. ; and dykes of the same rocks 

 also intersect the shales at frequent intervals. "Within the pipes 

 there are unaltered nodules of the same dolerite. With regard to 

 the relation of the diamonds to the rock of the pipes in which they 

 are found, the author stated that he thought it probable that the 

 latter was only the agent in bringing them to the surface, a large 

 proportion of the diamonds found consisting of fragments. At 

 the same time he remarked that each pipe furnished diamonds of a 

 different character from those found in other pipes. 



January 7th, 1874. — Prof. Ramsay, Y.P.R.S., Yice-President, 

 in the Chair. 



The following communications were read : — 



1. " The Origin of some of the Lake-basins of Cumberland." 

 —First Paper. By J. Clifton Ward, Esq., E.G.S., Assoc. R.S.M. 



After referring to the fact that the question of the origin of lake- 

 basins cannot be satisfactorily discussed unless the depth of the 

 lakes and the heights of the mountains are brought before the 

 mind's eye in their natural proportions, the author sketched out the 

 physical geography of the lakes under discussion (Derwentwater, 



