446 Dr. E. Frankland. On the Conditions [Mar. 21, 



enormous number (56,630) of microbes. In the following month of 

 February, however, this number was reduced to about 7,000, although 

 the amount of sunshine was not very much greater. In the following 

 month of March, there was a great increase both of sunshine and 

 bacteria, whilst in April, there was an increase of sunshine and a 

 great diminution in the number of microbes. In May, however, 

 there was a great decrease of sunshine, but a very slight increase of 

 microbes. In June there was rather less sunshine than in the 

 previous month, but also fewer microbes ; whilst in July, an increase 

 of sunlight was accompaned by an increase of microbes. In August, 

 September, and October, with each diminution of sunshine there was 

 a corresponding increase of microbes ; but in November, with a very 

 moderate amount of sunlight, there was an enormous increase of 

 microbes from 3,800 to 20,080 per cubic centimetre, whilst in the 

 following month of December a considerable diminution of sunlight 

 was found to be compatible with a marked decrease of microbes. 



Thus it is evident 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 

 presented in the following table and diagram (pp. 447, 448). 



This table and diagram show very conclusively that the volume of 

 water flowing in the Thames is the paramount influence determining 

 the number of microbes in the water. They compare the volume of 

 water in the river, as gauged at Teddington Weir, with the number 

 of microbes found in the raw Thames water at Hampton on the same 

 day. In the diagram, the numbers representing the flow of the river 

 in millions of gallons and the number of microbes per cubic centi- 

 metre of water both run from the bottom of the diagram upwards. 



Comparing the numbers in the table and the curves on the diagram, 

 it is seen that, with a few exceptions, a remarkably close relation is 

 maintained between these numbers and curves respectively ; thus 

 during the months of May, June, July, August, September, and 

 October, 1892, the river was low and the number of microbes small. 

 In December of the same year, the daily flow of the river had risen to 

 2,105 millons of gallons, and the microbes to 11,158 per cubic centi- 

 metre ; whilst in January 1893, the flow had decreased to 915 millions 

 of gallons, and the microbes to 8,210 per cubic centimetre. In February 

 of the same year, the flow of water over Teddington Weir had risen to 

 3,255 millions of gallons, and the number of microbes simul- 

 taneously to 13,947 per cubic centimetre ; whilst in March, with a 

 reduced flow of 1,175 millions of gallons, the number of microbes 

 came down to 3,737 per cubic centimetre, and this was followed in 

 April by a further diminution to 1,763 per cubic centimetre, whilst 



