Geology 



there is experimental proof that sodium chloride and 

 magnesium chloride, both of which are present in sea 

 water, do produce a flocculation and a consequent pre- 

 cipitation of tiny mud particles suspended in water, and 

 this action undoubtedly accounts for the deposition in 

 estuaries of a large quantity of mud and silt which would 

 otherwise be carried out to sea. It is of interest in this 

 connection to note that compounds of aluminium, such 

 as ordinary alum, are of use to purify water from sus- 

 pended matter so as to render it fit for drinking or other 

 purposes. 



On arriving near the head of the estuary, we saw 

 that it narrowed rapidly, and we soon found ourselves 

 sailing up the river, between high banks of silt, covered 

 with grass and other dwarf vegetation, which prevented 

 our getting a view of the country from the deck of the 

 steamer. 



Along the banks were a few farmhouses surrounded 

 by poplar trees, and here and there a windmill of the 

 modern circular type, such as was often used at home 

 for the purpose of pumping water. 



Houses, windmills, and trees all appeared to rise from 

 land some feet lower than the river banks, and on 

 ascending an iron ladder attached to one of our funnels 

 we saw that this was indeed the case. 



On first thoughts, it would seem that the embank- 

 ments on the sides of the river had been constructed by 

 man to prevent the overflow of the waters on to the low- 

 lying country beyond. The embankments, however, 

 appeared to be of great size and thickness, and showed 

 no signs of recent work having been done upon them, 

 and, furthermore, the country was still but sparsely 



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