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



found in winter or when the temperature of the water was low, and 

 the lowest in summer or when the temperature was high. 



Amongst the conditions which favour or retard the development 

 of microbial life in river water, temperature, rainfall, and sunshine or 

 gloom are probably the most important, sunshine having been 

 recently shown by Dr. Marshall Ward to be, under certain circum- 

 stances, extremely potent in the destruction of bacteria. The 

 following tables contain the results of these microbe determinations 

 placed in juxtaposition with (A) the temperature of the water 

 at the time the sample was taken, (B) the number of hours of sun- 

 shine on the day and up to the hour when the sample was drawn 

 and on the two preceding days, and (C) the flow of the Thames over 

 Teddington Weir on the same day expressed in millions of gallons 

 per 24 hours. 



The samples for microbe cultivation were collected at about 9 in. 

 below the surface of the water in partially exhausted and sealed 

 tubes, the ends of which, when the tubes were lowered to the desired 

 depth, were broken off by an ingenious contrivance devised by my 

 assistant, Mr. W. T. Burgess. On being withdrawn from the river, 

 the tubes were immediately hermetically sealed and packed in ice 

 for conveyance to my laboratory, where the cultivation was always 

 commenced within four hours of the time of collection. 



For the records of sunshine I am indebted to the kindness of Pro- 

 fessor E. J. Stone, M.A., F.R.S., the Radcliffe Observer at Oxford, 

 and to Mr. James B. Jordan, of Staines. Finding that the Oxford 

 observations differed but little from those at Staines, and as Staines 

 is nearer to, although higher up, the river than the place where my 

 samples were collected, I have used the Staines records in the table, 

 except on a few dates when Mr. Jordan's observations had been 

 intermitted. 



The gaugings of the Thames at Teddington Weir were kindly 

 furnished by Mr. C. J. More, the engineer to the Thames Conservancy 

 Board. 



Without the data giving the conditions of sunshine and flow of the 

 river, it was impossible to draw any trustworthy conclusion as to the 

 cause of the increase and diminution of the number of microbes per 

 cubic centimetre of Thames water at Hampton, because the condi- 

 tions supposed to be favourable for microbial life all, approximately, 

 attain the greatest intensity at the same season of the year ; thus, 

 whilst the temperature is lowest in winter, so also, as a rule, are the 

 minimum amount of sunshine and the maximum amount of flood 

 water. The following collateral observations, however, afford definite 

 evidence as to which of the three conditions temperature, sun- 

 shine, and flow of the river has the predominant influence upon 

 bacterial life in the water. The first table and diagram compare the 



