Minutes of Proceedings. xxxvii 



This mass of rock, about a mile in thickness, has been entirely 

 removed over the whole area of the mountain ranges of the coast. 

 Matroosberg, for instance, if it had not been subjected to weathering, 

 would have been 12,000 feet high instead of 7,000 feet. In the 

 Malmesbury clay-slate valleys, where the Table Mountain sandstone 

 has also been removed, we must add 4,000 to 5,000 feet of rock to our 

 aggregate. In the Tulbagh Valley, ending at Breede Eiver Station, 

 432 cubic miles of solid rock have been washed out, not counting 

 that underlying the Table Mountain sandstone. One cubic mile of 

 rock weighs about 7,000 millions of tons, so that an estimate may 

 be got of the whole amount that has been denuded from this small 

 tract of country. In applying all this to the alteration of sea-level, 

 we know that water is attracted by the mass of the moon, which is 

 the cause of tides. In the same way the mass of the continents 

 exert a pull on the waters of the sea. Fischer first pointed this out, 

 and Listing calculated constants for various places ; thus he gives : 

 Berlin, 37"7 M. ; London, 118 M. ; Paris, 268 M. ; St. Helena, 

 847 M. ; that is, if the land masses were absent in these places 

 the sea-level would be so many metres lower. If now an enormous 

 mass of material is removed from a continent, as it has been in South 

 Africa, there is less matter to attract the water, and the sea-level 

 must consequently sink. The material that is taken from the land 

 is deposited at the bottom of the sea within two hundred miles of the 

 coast, so that the difference of attraction on the whole mass of the 

 ocean is not great ; but water being a fluid, that round the coast 

 obeys the attraction of the land mass immediately near it, and if 

 larger portions of this are removed the sea-level must sink. Thus 

 without bringing in any earth movements we can explain the 

 -deserted sea beaches around our coasts. Whether the sea-level is 

 actually sinking is another matter, and we have not yet materials 

 for determining it. Earth movements may be going on that are 

 increasing or compensating the sinking due to loss of attraction, but 

 the latter is a factor in the sum total. I have brought these few 

 remarks forward to show the sort of problems that are always before 

 us apart from the dry routine work of map and specimen-collecting. 

 Dr. Corstokphine criticised Mr. Sehwarz's view that there was 

 still an uplifting taking place in the Zwartebergen, the evidence of 

 the river kloofs being in his opinion insufficient. It was also 

 pointed out that we have no evidence of any repeated uplifts of the 

 mountains here, such as are shown by the Alps, and reference was 

 made to the vastly different conditions the country would be in had 

 nature been more generous of such movement in this part of the 

 world. With regard to the main part of the paper, Dr. Corstorphine 



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