part 2] ANNIVERSARY ADDRESS OF THE PRESIDENT. lxxi 



either Ordovieian or Silurian in age. Archaean tillites occur in 

 South Australia, containing erratic blocks up to 10 feet in diameter 

 in beds 1500 feet thick. It is but fair to state that the glacial 

 origin of these beds, though accepted by Sir T. W. Edgeworth 

 David, Prof. W. Howchin, and other geologists, is denied by 

 Dr. H. Basedow with a confidence which fails to carry conviction. 

 In some parts of the Archaean world the climate was arctic rather 

 than tropical. 



In Montana it is estimated that there are upwards of 30,000 feet 

 of unaltered sedimentary strata between the older Archaean rocks 

 and the Cambrian System. It is a remarkable fact that, while 

 marine Cambrian sedimentary strata have yielded a rich harvest of 

 animal fossils, thousands of feet of practically unaltered Archaean 

 rocks are almost completely barren. The Yindhyan S3 r stem of 

 India, over 1400 feet thick, made up of sandstones, frequently 

 ripple-marked and sun-cracked, shales, and limestones, occupying 

 much the same position in the geological series as the Torridonian 

 of Scotland, is characterized by an almost complete absence of 

 fossils. The absence of marine life, save a few fossils of doubtful 

 value referred to the Algas, in the enormous thickness of the Late 

 Archaean series exposed in the Grand Canon and in other places 

 which have been searched during the last thirty years, although it 

 has been attributed to the obliteration of any fossils that may 

 have been present by the destructive action of heat, cannot be thus 

 explained. 



It is noteworthy that records of animal life in Archaean seas are 

 not above suspicion : Dr. C. D. Walcott instituted the generic 

 name Beltina for crustacean fragments said to be Algonkian in 

 age ; but Dr. R. A. Daly favours a Cambrian horizon for the 

 Beltina Beds. Prof. L. Cayeux recorded many Pre-Cambrian 

 foraminifera and other organisms from Britanny, but H. Rauff 

 denied their organic nature. In the British Isles, in China, India, 

 and in many other parts of the world the Pre-Cambrian rocks are 

 ecpially barren. Evidence is not lacking that much of the Upper 

 Archaean sedimentary material was accumulated on land and not 

 under water, and in an arid climate. Attention has often been 

 called to the remarkable freshness of the felspars in the Torridonian 

 grits of the North-West Highlands, which suggests a rapid 

 disintegration rather than decomposition by chemical action. 

 Dr. B. N. Peach and Dr. J. Home conclude that the climate was 

 probably cold, and that there were periodic floods of great intensity. 



