150 OLDHAM: SANDHILLS OF CLIFTON NEAR KARACHI. 



out to a greater depth than that which had been formed by natural 

 scour. 



A sample of sand collected from the shore at Clifton, just above 

 high-water mark, had the following constitution : — 



Left on sieve No. 24 



• 



. i'o per cent. 



» 5° • 



. 



. l6'o „ 



70 ' 



• 



• 33'o 



„ 100 . 



• 



■ 39"5 



Passed through 100 . 



. 



. 10-5 „ 



The constitution of this sample is not unlike that of the dredgings 

 Nos. 1 and 2, the differences being easily accounted for by local cir- 

 cumstances. The sample was collected from just above high-water 

 mark, and consists of material which has been blown up from the shore 

 by the wind ; hence the absence of the larger fragments of shell, which 

 remain on that part of the shore reached by the waves. 



It is from this that the sand composing the sandhills behind Clifton 

 is derived. Two samples, one taken from the windward slope, the 

 other from the steep lee slope of the principal sandhill, gave the follow- 

 ing composition : — 





Windward slope. 



Lee slope, 



Left on sieve No. 50 . 



. 



. I'O 



. 



„ 7° • 



. 



. 26'0 



• 8- 5 



„ 100 . 





. 560 . 



. 7S'o 



Passed through 100 . 



. 



. i7'o 



• 13-5 



The sorting effect of the wind is well seen here, all the coarser 

 fragments have been left behind, and disappeared, and those grains 

 which pass through a sieve of 70 meshes to the inch, but not through 

 one of 100, amount to more than half of the whole bulk ; this sorting 

 effect has been carried still further in the material forming the lee slope, 

 where grains of this size form over three-quarters of the whole bulk. 



The sands, both of the shore and of the sandhills, are composed to 



a large extent of fragments of shell. In the case of the sand from the 



shore this was found to amount to 66*25 per cent., and in the case of 



the sand of the sandhills, to 53-5 per cent, of the total weight. The 



( 18 ) 



