7 July, 19 t 2.] lufiioicc of Radio- Active Mineral, ^'c. 



4rc^ 



traces were detected in A and B, there were doubtful traces of formaldehyde 

 in the distillate from C and G, and none at all in those from E', E, and F. 

 Apparently, however, in the presence of bacteria, carbon dioxide and water, 

 the rays from a radio-active mineral present in sufficient quantity are able 

 to cause a formation of small amounts of formaldehyde. The cultures 

 were in darkness during the whole of the time, so that the action could not 

 be due to the influence of ordinary light energy. 



Whether the retarding action is a direct one, or is due to the formation- 

 of traces of formaldehyde is not quite certain, but the amount producedof 

 the latter seems to be altogether too small to wholly explain the retarding 

 action. In any case, however, a strong retarding action is exercised, but 

 onlv if a relatively large amount of the mineral is used, and it remainedto 

 be determined whether any pronounced action was exercised in the field with 

 dressings of radio-active mineral applied in the quantities customary for 

 other mineral manures. Accordingly, samples of the soil were collected 

 from the field plots, three months after sowing, and the numbers of the 

 bacteria present determined. From each o"f the quarter-acre plots forty- 

 samples of soil were taken, and thoroughly mixed together. Five grams 

 of the mixture were then shaken up with 40 c.c. of sterilized water, allowed 

 to settle for five minutes, and then ^V of a c.c. of the water inoculated 

 on to gelatine plates. The number of organisms developing on the plates 

 at 20 degrees centigrade was counted, and hence the number of the organ- 

 isms present in a c.c. of the .soil was calculated. These tests were carried 

 out bv Dr. Bull in the Bacteriological Laboratory at the Melbourne 

 University. The following are the results: — 



Number of 



Organisms, 



one c.c. 01' Soil. 



Small plot, 9 square yards — 



A. i lb. radio-active mineral 

 per square foot* 



One-third acre plots — 



B. No manure 



C. 1 cwt. radio-active mineral 

 per acref 



D. .56 lbs. superpliosphate per 

 acrej 



LONGERENONG PlOTS. 



17,250,000 



750,000 

 900,000 

 1,800,000 



Many liquefying organisms 



Fewer liquefying than non-liquefy- 

 ing organisms 

 Numerous Uquefying organisms 



Bacillus coli-communis present, 

 very numerous liquefying or- 

 ganisms 



Small plot, 9 square yards — 



A. J lb. of radio-active mineral 

 per square yard* 



Quarter- acre plots — 



B. 59 lbs. superphosphate and 

 56 lbs. radio-active mineral 

 per acref 



C. 1 cwt. radio-active mineral 

 per acre-j- 



D. 59 lbs. superphosphate per 

 acrel 



RUTHERGLEN PlOTS 



450,000 



1,125,000 



1,800,000 

 1,800,000 



Liquefying and non-liquefying: 

 organisms and ten moulds 



Less liquefving organisms than- 

 on D. 



More liquefymg organisms than 

 on D. 



Applied as top dressing. 



t Drilled in with the seed. 



