Rev. J. F. Blake — Form of Sedimentary Deposits. 15 



from a uniform vertical sheet of sediment will continually thicken 

 distally, till the highest particle reaches the bottom, when it will 

 end abruptly. The deposit thus falling from the bottom of the 

 current will be reproduced at any depth where it reaches the solid 

 bottom of the sea below. 



Fig. 2. 



-The Distribution on the Sea-bottom of 

 Uniform Sediment. 



A Vertical Sheet of 



a-e, the vertical sheet ; b-b'-b" etc., the paths of particles ; a"'-e"', the deposit built 

 up by successive sheets. 



We must now see whether and how far this result may be 

 modified by other causes. The rising of fresh water over salt will 

 increase the rate of deposition, since the bottom of the current, 

 instead of being horizontal, will curve upwards and so cut more 

 lines of flow. The mixing of sea- water will have the same effect, 

 as the resistance to sinking is known to be less in salt water than 

 in fresh. Evaporation will have little effect, because the detritus 

 will soon leave the surface. But all these causes increase in 

 efficiency with time, and thus will accentuate the thickening of 

 the deposit with increase of distance from the source of supply. 

 On the other hand, the greater velocity of the stream in its centre 

 would diminish the thickening ; but this, when the sea is reached, 

 is transformed into a special peculiarity, as will be seen further on. 



The most important modification is the following. If a mass 

 of water in motion is retarded in the direction of its flow it must 



