41 8 Journal of Agriculture , Victoria. [lo July, 191 2. 



of radio-active mineral in tlie soil injuriously affected the development of 

 useful soil bacteria, it might, on the whole, injure the final harvest, 

 although it favoured the early stages of germination. 



In order that these questions might be answered by a trial in the field, 

 the Council of Agricultural Education consented to the establishment of 

 test plots at Longerenong, and the Lirector of Agriculture to a series of 

 similar plots being used for the tests at Rutherglen. I have to thank Mr. 

 Sinclair, the late Principal of the Longerenong Agricultural College, and 

 Mr. Adcock, Principal of the Viticultural College, Rutherglen, for the 

 interest they have taken in these experimental plots. 



The Influence of Radio-Active Mineral on the Development 



OF Bacteria. 



The first point to be determined was the amount of radio-active mineral 

 required to influence the development of soil and other bacteria, or if any 

 action at all was exercised. To determine this, a series of flasks each con- 

 taining 100 c.c. of nutrient bouillon were each infected with i c.c. of a 

 watery extract from garden soil, and kept at a temperature of approxi- 

 mately 15 degrees centigrade. At the end of fourteen days -Jq of a c.c. 

 was withdrawn from each, and added to 50 c.c. of sterilized water. The 

 same quantity of this mixture was then transferred to a gelatine plate 

 culture, and from the number of organisms developed upon the plate, the 

 number per c.c. of the culture fluid was estimated. The results were as 

 follow : — 



These results show that bacteria are able to develop even in the presence 

 of large quantities of radio-active mineral, but that, nevertheless, a distinct 

 retarding action is exercised which becomes more pronounced with longer 

 exposures. 



Liquefying organisms were relatively more abundant in A, B, and C, in 

 the order given than in the other cultures. Possibly organisms of the 

 ■bacillus subtilis type may be more resistant to the rays of radio-active 

 mineral than are other bacteria. 



That the retarding influence was really due to the rays of the mineral 

 and not to any poisonous substance dissolved from it is shown by experi- 

 ment G. 



The flasks were then sealed, and opened after two months. The liquid 

 •contents were distilled, and the distillate tested for formaldehyde. Faint 



