Report on the Jlacteriology of Water. 403 



Doubling Periods. 



This is a good opportunity for explaining more in detail what is 

 meant by the above term. 



If this long and symmetrical curve 83 is carefully examined, it will 

 be found that, over a great part of its course, any chosen short length of 

 the filament doubles its length in approximately equal times. 



Thus it took forty. five minutes to grow from 9 /* to 18 ft, and the 

 same from 18 [i to 36 /*, and so on. But it is practically the same 

 whatever the length we select, provided the conditions are constant, as 

 will be seen by comparing the curves. 



I term the period required for doubling the length the " doubling 

 period," and the comparison of a large number of curves shows that 

 the nearer we approximate to absolute constancy of the conditions 

 the clearer the truth of the following statement, which amounts to a 

 law, is evident. 



Whatever the length of the filament taken, that length is doiibled in 

 equal times when the conditions are constant. 



For the present it is only necessary to clearly apprehend the 

 meaning of the above term, and the general truth enunciated, so that 

 i he reader can understand the figures attached to the tables. Further 

 particulars will come out as we proceed. 



The following experiment at 30 was carried out on July 18. The 

 spores, in stiff weak gelatine, were sown and put in the Sachs' box 

 at 9.30 A.M. 



The temperatures ran as follows : 



Temp. 

 Time. C. 



9.30 A.M. = 30-5 



10.0 = 31-5 



L0.20 = 30-6 



10.30 = 30-2 



11.0 = 3025 



11.20 = 30-4 



11.35 = 30-5 



12.0 noon = 31'0 



12.15 P.M. = 31-1 



12.30 = 30-5 



1.30 = 30-0 



1.45 ,, = 24'75 (due to opening box to arrange) 



1.47 = 27-0 



1-51 = 29-0 



2.0 = 30-0 



2.30 ., = 31-0 



3.15 = 31-0 



