274 H. B. Maufe — Coastal Series of Sediments, E. Africa. 



whose weathering furnished the hundreds of cubic miles of mud and 

 sand of the sedimentary rocks have likewise vanished. There must 

 have been thousands of feet of solid rock beneath the seas and the 

 continents of the time, but these seem to have been melted and set in 

 motion as the materials of the batholithic granites and syenites that 

 came later. The batholiths have even stoped down and encroached 

 upon the lower portions of the Coutchiching, Keewatin, and Grenville 

 as well ; so that to find the original thickness of the first known 

 crust of the earth one must add many thousands of feet to the estimates 

 given above. 



Finally, it must be recalled that water existed as a liquid at the 

 very beginning. The rocks forming the basins were not warm enough 

 to evaporate the seas of the time ; and in both the Keewatin and the 

 Grenville there are important beds of sediments containing five or ten 

 per cent of carbon, strongly suggesting algae or some other form of 

 plant life. It may be that the limestones also were formed by the 

 aid of plants or animals. If life existed in the seas, as seems very 

 probable, the temperature of the earth's surface was not higher than 

 living beings can endure, and we may fairly assume that conditions 

 were not widely different from those of later geological periods. 



With conditions such as have just been described in early Archaean 

 time there is no good reason to suppose that the molten magma was 

 near the surface. It was probably as far below as in later ages or at 

 present. The great abundance of Archaean granites and orthogneisses 

 simply means that, in the most ancient regions of the world, erosion 

 has gone to greater depths than elsewhere. The same types of 

 plutonic rocks are found at many later ages, though naturally they 

 are not so extensively exposed, since the overlying rocks have under- 

 gone less destruction. Batholiths of Mesozoic granite and diorite 

 cover 50,000 square miles of the coast ranges of British Columbia 

 and have precisely the same habit as the Laurentian. There is, in 

 fact, no geologic reason for supposing that the earth had a higher 

 temperature in the Archaean than at any later time. If the earth 

 was ever a molten globe it had so far cooled down in the earliest 

 known geological times that life probably existed, that water and 

 air did their work just as in later ages, and that an immense thickness 

 of sediments and lavas could be deposited on a firm foundation of still 

 earlier rocks. 



VI. — The Coastal Series of Sediments in the East Africa 



Protectorate. 



By H. B. Maufe, B.A., P.G.S., Director of the Geological Survey of 

 Southern Bhodesia. 



IN his report on "The Coal Resources of the East Africa 

 Protectorate " published in the Twelfth International Geological 

 Congress' The Coal Resources of the World (vol. ii, p. 381), Dr. J. W. 

 Evans discusses evidence bearing on the existence of coal in the Taru 

 Grits, which form the lowest member of the coastal series of sediments 

 in the East Africa Protectorate, lief erring to a report of mine, 1 he 



1 Beport relating to the Geology of the East Africa Protectorate. Colonial 

 Reports, Miscellaneous, No. 45, 1908. 



