5G 



Dr. Edward Franldaml 



[Feb. 21, 



is from mountain sources, is above all susiDicion of this kind. TLese 

 otlier causes have during the last ten years been much mitigated in 

 London by various sanitary improvements ; whilst, as shown in the 

 diagram (Fig. 1), there has been no corresponding mitigation in 

 Manchester. In this diagram the continuous dotted line shows the 

 mortality per 100,000 of population from typhoid in Manchester, 

 and the crossed broken line the death rate from the same disease in 

 London ; whilst the faint broken line represents the degree of tur- 

 bidity of river water delivered in London. 



Although, very soon after the year 1856, all the water supplied 

 to the metropolis was obtained from sources much less exposed to 

 drainage pollution, it was still very carelessly filtered. Previous 

 to the year 1868, there are no records of the efficiency, or otherwise, 



TTPK» M LONDON AND MANCHESTER CONTRASTED WITM TURBIDITY. 





Fig. 1. 



of the filtration of the metropolitan water supply derived from 

 rivers as distinguished from deep wells, the w^ater of which is per- 

 fectly clear without filtration. 



It was in the year 1868 that I first began to examine the water 

 sup2)lied to the metroj)olis from rivers with reference to efficiency 

 of filtration. In that year, out of eighty-four samples examined, 

 seven were very turbid, eight turbid, and ten slightly turbid, so that 

 altogether no less than nearly 30 per cent, of the samj^les were those 

 of inefiiciently filtered water. The metropolitan water supply, then, 

 up to the year 1868, may be shortly described as derived, for many 

 years, from very impure sources, with either no filtration at all, or 

 with very inefficient filtration ; and afterwards, when the very impure 

 sources were abandoned, the supply was still often delivered in a 

 very inefficiently filtered condition. But, after the establishment of 

 monthly reports on the filtration of the river-derived supplies, the 



