350 E. M. KINDLE 



of our eastern counties [England] tends to travel at the same rate 

 as the coast is cut back. " 



Observation of surface currents alone will afford no positive 

 evidence concerning the direction in which bottom formations are 

 growing, nor their source. On the shoal east of Gorda bank the 

 direction of the flow is nearly at right angles to the surface current. 

 North of Barbados 60 miles Pilsbury' found at different levels 

 between the surface and 200 fathoms, currents flowing in three 

 different directions, simultaneously the lower at right angles to 

 the surface. 



Relative aridity. — The average annual loss by erosion is 95 

 tons for every square mile of the United States, excluding the Great 

 Basin, according to an estimate published by the U.S. Geological 

 Survey. The enormous volume of sediment which this con- 

 tribution from nearly 3,000,000 square miles yields is distributed 

 around the continental shelf of North America with a degree of 

 irregularity corresponding to a number of variable factors. Among 

 these factors are the variability in the rate of rainfall, location of 

 river mouths, the direction and velocity of air currents, and the 

 strength and direction of tidal currents. The interplay of all these 

 and of various other factors will doubtless result in building on 

 parts of the continental shelf deposits of great thickness and very 

 considerable extent. Over other extensive areas nothing at all 

 will be left by the ocean currents, and scour may result. The 

 general result may be an irregularity of deposition as great as that 

 which characterizes wind-blown deposits. 



The comparatively small volume of elastics which an arid region 

 like western Australia could furnish to its extended littoral zone 

 would result in a minimum rate of deposition which would probably 

 be much lower than that of any other continental coast line. This 

 vast region which is essentially a desert coast line of about 3,500 

 miles has not a single river of any size. The so-called rivers 

 are mostly insignificant streams many of which are nearly dry 

 unless during the rainy season.^ 



'Pilsbury, "The Gulf Stream; Methods of the Investigations and Results of the 

 Research," Rept. U.S. Coast and Geol. Survey (1890), Appendix 10, p. 570. 



^ Henry M. Cadell, "Some Geological Features of the Coast of Western 

 Australia," Edinburgh Geol. Sac. Trans., VIII (1899), 174. 



