(j6 



Dr. Edward Franhland 



[Feb. 21, 



has been exposed. The diagram is constructed on the same lines as 

 the first. 



It is evident, therefore, from this comparison that, as in the case 

 of temperature, there is some other condition which entirely overbears 

 the influence of sunlight in the destruction of microbes in the river 

 water. This condition is the amount of rainfall higher up the river, 

 or, in other words, the volume of water flowing along the river bed, 

 as is seen from the comparison represented in the next diagram 

 (Fig. 15). 



Fig. 13. 



This diagram shows very conclusively that the volume of water 

 flowing in the Thames is the paramount influence determining the 

 number of microbes. It compares the volume of water in the river, 

 gauged at Teddington Weir, with the microbes found in the raw 

 Thames water at Hampton on the same day. In this diagram, the 

 numbers representing the flow of the river in millions of gallons per 

 day and the number of microbes per c.c. in the water, both run from 

 the bottom of the diagram upwards. 



