170 



SCIENCE PROGRESS. 



is seen from the diagrams Nos. 3, 4 and 5, which show the 

 proportional amounts of organic elements in the raw and 

 filtered waters ; they also show the advantage of storage 

 in excluding flood water, No. 4 shows that floods in March 



PROPORTIONAL AMOUNT OF CRCANIC ELEMENTS 

 IN THAMES WATER 



-■ ■» ' * . XT 



No. 3. 



arid August were circumvented, but not in November. The 

 numbers in the margins of the diagrams express the pro- 

 portional amount of organic elements, that in the Kent 



PROPORTIONAL AMOUNT OF ORGANIC ELEMENTS 

 IN RAW LEA AND EAST LONDON COMPANY'S WATER 



7 

 6-0 

 S-0 

 4-0 

 3-0 

 2-0 

 1-0 



No. 4. 



Company's water during the nine years ending December 



1876 being taken as unity, as is depicted in diagram No. 5. 



Hitherto I have spoken of chemical purity or comparative 



freedom from organic matter only, but the spread of diseases 



