lxxii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [vol. lxxix, 



Prof. J. Walther compares Torridonian conditions with those of a 

 modern sub-tropical desert where icy storms alternate with tropical 

 rains. Pehbles from the Torridon grits, and from strata of similar 

 age in Sweden, bear the impress of the action of sand-blasts. The 

 frequent occurrence of red deposits in different Archaean regions is 

 adduced as further evidence of a dry climate. 



A land bare of vegetation, mountain-sides exposed to the 

 destructive influences of sharply - contrasted day and night 

 temperatures, avalanches of rock, restlessly drifting sand-dunes, 

 floods following torrential rains spreading the disintegrated rock 

 and wind-blown sand in fans and sheets in the valleys : if the 

 conditions were even approximately such as these, it is hardly 

 surprising that we search in vain for the remains of a land- 

 vegetation. But deserts, although probably of vast extent, were 

 not a universal feature of Archaean continents. The unfossiliferous 

 condition of vast piles of sedimentary strata is significant, and it 

 is in the highest degree improbable that, if there had been a 

 vegetation, some relics of it would not have been preserved. 



Greological literature contains many references to indirect evi- 

 dence of plant-life during the latter part of the Archaean Era, and 

 a few descriptions of supposed plants. In some parts of the world 

 carbonaceous rocks and beds of graphite are developed on a com- 

 paratively large scale. In the district of Lake George (New York), 

 alternating layers of graphitic shale or schist form beds from 3 to 

 13 feet thick, described as ' a fossil coal-bed ' : on the analogy of 

 the nature of more recent coal-seams, the oldest graphitic beds are 

 considered to afford evidence of the occurrence of contemporary 

 vegetation, possibly, it has been suggested, of ' primitive marine 

 plants '. The presence of graphite is not, however, in itself proof 

 of the existence of vegetation. Dr. C. E. Tilley has recently dis- 

 cussed the origin of graphite in Pre-Cambrian rocks in South. 

 Australia and other regions : while he believes that a sedimentary 

 origin of the Australian graphite is most closely in accord with 

 the facts, he also recognizes the possibility of the formation of 

 graphite by the reduction of oxides of carbon by hydrogen. A car- 

 bonaceous deposit in Finland, which reaches a thickness of about 

 6g feet, and is almost pure carbon, is described as undoubtedly organic 

 in origin ; but, if organic, we cannot tell whether it be animal or 

 vegetable. In some fine-grained carbonaceous rocks in Finland of 

 Archaean age, which are believed to be metamorphosed sediments, 

 small bodies like empty sacs, crushed and distorted and outlined in 



