56 Transactions of the South African Philosophical Society. 



free of any trace of gold, yet the gravels contain appreciable quan- 

 tities, and such deposits have been worked from time immemorial ; 

 in a sandstone formation one, therefore, always looks to a banket or 

 conglomerate bed as the one most likely to contain the precious 

 metal. 



The whole problem of the Karroo gold amounts to this : it is 

 unlikely that reef gold occurs in the Karroo, while it certainly exists 

 in the Table Mountain Sandstone of the Zwartebergen ; by the 

 knowledge that the localities where the gold is now obtained were 

 once connected by a graded plain cut by rivers flowing north from 

 the Zwartebergen, we have an adequate explanation of how the gold 

 was carried from the one place to the other. There are no gravel 

 caps to the hills on the Karroo gold-fields, and all signs of the flat 

 ground have disappeared, but once the gold got to the place and the 

 levelled hills became cut into the kopjes as they now are, the gold 

 on top would sink with the sinking of the valleys, and instead of 

 being carried off with the lighter sand, would be left behind and 

 come to rest in the crevices of the rock, just as in actual sluice- 

 boxes the gold grains come to rest in the furrows of the shoots. 



The problem of the high-level gravels is one of altitude, and there 

 are too few bench marks in the Colony to make any reasoning of the 

 above sort perfectly satisfactory. I have throughout had to use 

 rough estimates and calculations from bench marks up along 

 assumed rates of increase in the falls of the rivers. It would be of 

 very great value not only from a theoretical standpoint, but also from 

 a practical one as well, if three or four carefully levelled sections 

 were run from the coast inland ; not only would we be able to dis- 

 cuss such apparently trivial things as the existence in past ages of 

 old land surfaces, but one could gather from such sections a true 

 idea of the present fall of rivers, and once that was obtained, we 

 should no longer be in doubt about the various irrigation schemes 

 that are continually being proposed — we should have solid data on 

 which to base our estimates. 



