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TROPICAL HYGIENE, SANITATION, ETC. 



Mechanical sand fillers are as the above but smaller and con- 

 structed of iron or steel, with pressure to hasten the process. Sulphate 

 of alumina. 2 gr. per gallon (o'i2 grm. per 4*5 litres) is added to form 

 an artificial film on the surface. 



The pressure is by compressed air, the pressure being reversed 

 and often steam applied for the cleansing process. 



The rate of filtration is about fifty times greater than the slow 



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Diagram of a section of a 

 sand filter. 



GRAVEL 



WASTE PIPE 

 CONNECTING WITH 

 SEWER 



Diagram of a mechanical filler. 



sand filter. Such filters have proved useful at Alexandria and Mvsore, 

 where the water is turbid. They are largely used in the States of 

 America where the river water is heavily charged with suspended 

 matter. 



It is often necessary to cleanse washing wafer as for troops in the 

 field. The following method as practised by Norman Goode and 

 Basil Hughes has proved useful to such an extent that the same water 

 can be used an unlimited number of times. 



The soapy water runs from the bath house into a mixing tank. 



