318 CONDITIONS OF DEPOSITION 



glomerates at the bottom, then fine-grained rocks of 

 fluviatile origin, and, finally, marine beds on the top. 

 During the uniform and gradual depression of a tract of 

 country, in the course of which the actual grade or 

 inclination of the river valleys would not be altered, 

 those parts of the valleys left above the level of the sea 

 at any one time would naturally be able to carry on 

 their work as they did before the downward movement 

 set in. In the case of the Uitenhage beds, however, the 

 state of affairs is quite different, no such regular spread- 

 ing of the deposits from the marine area is noticeable ; 

 on the contrary the Uitenhage district is the only one 

 where a series of conglomerates, fluviatile sands and 

 muds and marine beds has been observed, and even 

 there the red conglomerates and sands near the native 

 location at Uitenhage are intercalated with by no means 

 the lowest of the marine beds, showing that a part of 

 the shore of the sea lay round the end of the mountains 

 near Uitenhage some time after the earliest marine beds 

 were formed in the neighbourhood. If the sea ever 

 reached the western outliers of Oudtshoorn, Heidelberg 

 and Swellendam, no trace of its presence has yet been 

 found, and in any case over 1,000 feet of non-marine 

 sediments were piled up before it did so. These filled 

 up the old valleys to the extent of at least 1,000 feet, 

 very probably to a much greater depth, possibly above 

 the level of the lowest passes over the Langebergen and 

 Zwartebergen. 



There is, however, another possible cause which 

 would account for the old rivers receiving more dtbris 

 than they could carry away, and that is the coming in 



