EXPERIMENTS INITIATED IN 1909 41 



posed (on a protected balcony facing the East), I 

 did not open any of them till six months had 

 elapsed that is, till last January. Then, and 

 during the first half of February, I examined the 

 contents of a large proportion of the twenty her- 

 metically-sealed tubes that had been heated only 

 to 100 C., and was much surprised at finding no 

 organisms in any of them. 



That first led me to support some difference in 

 the constitution of these solutions, and to make 

 inquiries as to whether the sodium silicate used 

 for the latter experiments was from the same stock 

 as that which had been sold to me and used in 

 1906. I was then informed that the supply of 

 last summer had come from a different stock; and 

 on comparing it with a small quantity of the old 

 preparation still in my possession, some distinct 

 differences between them were ascertained. I was, 

 therefore, induced to get supplies of sodium sili- 

 cate from several other sources, and to make many 

 comparative trials with solutions varying only in 

 the one respect that the sodium silicate was from 

 a different source. The results of these trials have 

 served to show that solutions made from a supply 

 obtained from Allen and Hanbury early in March 

 last, and heated only to 100 C. for ten minutes, 



