xcii POSTSCRIPT. 



chains. North of Tete there are gold washings; and the range 

 of the strata seems there to be nearly North and South. At 

 present I have no faith whatever in the above hypothesis; though 

 it led to one happy anticipation. But erroneous hypotheses 

 have sometimes done the same before. What we seem to know is — 

 that gold is chiefly found among palaeozoic rocks of a quartzose 

 type. And if gold be found, in detached nodules, or nuggets, 

 among such rocks, it must be itself of the palaeozoic age. Some 

 of the great physical agencies of the earth are meridional ; and 

 these agencies may possibly — and in a way we do not compre- 

 hend — have influenced the deposit of metals on certain lines of 

 bearing. It would therefore be very foolish to reject an hypothe- 

 sis absolutely, because we do not comprehend the reasons of it. 

 So long as our hypothesis represents known facts, it cannot do 

 much mischief; though even in such a case it may happen to be 

 the means of too much narrowing our inquiries. Thus, I think, 

 it would be an hypothetical misdirection to say, that a quartzose 

 palaeozoic rock cannot be auriferous, because its strike is not 

 nearly north and south. Experience must settle this point. 



The geological age of the vast overlying mass of red shale, 

 sandstone, and red conglomerate — which forms a great broad 

 table-land across the continent, and extends towards the North 

 through many degrees of latitude — is of primary importance to 

 the illustration of the old physical history of what now com- 

 poses Southern Africa. A few trunks of silicified trees are 

 mentioned as belonging to this great deposit. One of them is 

 allied to araucaria. But the fossils, so far as I have heard, have 

 settled nothing. For fossil trees allied to araucaria are found 

 among primary, secondary and tertiary rocks. Judging again, 

 on mere vague analogy, I should expect that the vast deposit 

 would turn out to be of an old mesozoic, or of a permian age. 



Should these conjectures, to which, however, I attach no 

 value, turn out an approximation to the truth, South Africa 

 will then, like Australia, be denuded of the greater part of 

 those grand European and British deposits we call mesozoic. 

 The same may be said of South America; and thus we may 

 seem to be almost shutting out from the Southern hemisphere 

 the noble monuments of past time which decorate the middle 



