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intense cold, the third distinctly glacial epoch in the long record of the South 

 African rocks — an epoch that is generally believed to be contemporaneous with 

 the glaciation that affected India, New South Wales, Argentina, and the Falkland 

 Islands in late Carboniferous or early Permian times. 



Not the least interesting chapter is that on " Tertiary and Recent Deposits," for it 

 is concerned with problems of denudation and accumulation under conditions of a 

 scanty rainfall, which may be paralleled more than once in the geological record 

 of the British Isles. 



The authors attribute the enormous denudation that has taken place in South 

 Africa in different geological periods mainly to fluviatile and glacial action, and in 

 spite of the fact that they recognise the work of the wind in local erosion and in 

 the formation of drei kanters in the Table Mountain Sandstone, they do not seem 

 to entertain the possibility that it may have been by far the most effective agent in 

 the removal of rock in South Africa, as it certainly has been in many parts of the 

 world, not excluding the United Kingdom, where plains of aeolian erosion have 

 probably been of greater importance than those of marine denudation. 



Very curious is the occurrence of salt-pans, not only near the coast, but in a 

 tract from the north of Calvinia, along the outcrop of the Dwyka Series, north- 

 eastward to Kimberley and Boshof, as well as on the same beds in Gordonia to 

 the north-west ; but they are not confined to this formation, either in Cape Colony 

 or in the Transvaal. The authors believe that they have been excavated through 

 the agency of the prevailing northerly or north-westerly winds, which form accumu- 

 lations of the resulting sand on the southern and south-eastern margin of the pan, 

 while the north-western rim is in some cases a cliff capped with the calcareous tufa 

 which covers the country. It is remarkable that very often round the edge of a 

 salt-pan, and occasionally even within it, fresh water can be obtained by digging 

 shallow pits. The authors believe that the salt may be derived from the Dwyka 

 formation, but Sir Thomas Holland has shown that the salt of the Sambhar Lake 

 in Rajputana has been blown in the form of impalpable dust more than four 

 hundred miles across the desert from the Arabian Sea by the south-west monsoon 

 winds. There seems no reason why a similar explanation should not hold for the 

 salt-pans of South Africa, though the distance to be traversed by the north- 

 western winds from the Atlantic would be in some instances nearly eight hundred 

 miles. 



It is to be regretted that the word laterite is apparently used in the popular 

 sense of superficial hydrated ferruginous deposits, instead of that of a decompo- 

 sition product of aluminium-bearing silicates, which contains free aluminium 

 hydrate. The latter definition includes, not only the original material to which 

 Buchanan first applied the name more than a century ago, but also what is 

 ordinarily known as laterite in India at the present time. The word has been 

 definitely accepted in this sense in Germany and France. 



The book is full of instructive matter for geologists of all countries, and it is 

 not its least merit that it will enable every one to read with keen interest and full 

 understanding the reports of the Cape Geological Commission, some of the most 

 valuable contributions to the geological literature of the present time. 



The map is remarkably clear and detailed, but it may be suggested that 

 another on the same scale, showing the orographical features of the country and, 

 if possible, the axes of the principal stratigraphical folds, would prove very useful 

 for comparison. It may be mentioned that in the section on p. 118 the letters E. 

 and W. are transposed, and the direction of that on p. 17 is not stated. 



John W. Evans. 



