H. A. Baker — Loose Arenaceous Sediments. 



467 



By means of the formula the speeds of the currents just competent 

 to transport various types of Thanet Beds material were calculated. 

 The velocities obtained may be regarded as minimum values for the 

 rates of movement of the water from which the Thanet Beds were 

 deposited. 



The localities mentioned in the second table being approximately 

 in alignment, from west to east, it is of interest to plot a graph 

 showing the relation between competent velocities and distances. 

 When this is done the points are found to lie on a curve of logarithmic 

 type, and when competent velocities are plotted against the 

 logarithms of the distances the points lie very nearly in a straight 

 line (see Fig. 8). In the case of the Pegwell Bay data, however, the 



Charlfeo 



GreenKirtje. ,^ 



(MounfsWoodJ 



Pc6w«ll Bay 



=6w«.llDay . 



10 10 30 lO SO to 



Fig. 8. 



point lies somewhat below the line, but this is what was expected. 

 The highest Thanet Beds seen at Pegwell Bay really belong to the 

 lower part of the deposit, and higher values for the Equivalent 

 Grade and competent velocity would have been yielded by a sample 

 from a higher level, had one been available. These results suggest 

 that we have here a hopeful line of research, the following up of 

 which may be expected to yield comparative results of a reliable 

 nature. 



In view of the influence of shore-lines upon marine currents, the 

 writer is of opinion that the construction of a map indicating the 

 competent current values for the Thanet Beds of the London Basin 

 could not fail to throw much useful light upon the question of the 

 origin and development of the great trough. 



The results of similar work upon the mechanical constitution of 

 the Woolwich and Reading and Oldhaven Beds are reserved for 

 future discussion. 



