The Effects of Radio-active Ores and Residues on Plant Life. 5 



With all but two of the consignments of radio-active material particulars 

 were furnished of the approximate amount of Radium Bromide each contained 

 per ton, and by careful calculation it was therefore possible to ensure an equal 

 application of Radium in almost every case. In the two instances where the 

 degree of radio-activity was not stated, the material was used at the strength 

 recommended by the vendors. 



It was clearly demonstrated in the 1914 experiments that, so far as any 

 beneficial result was obtained, a weak dressing of radio-active Ore was quite 

 as effective as a strong one, and this was taken into consideration in fixing the 

 standard for the 1915 tests. For the trials in pots (Series i) the dressing 

 given was approximately i/4,oooth of a milligramme of Radium Bromide to 

 a lo-inch pot containing about 15 Ibs. of soil. In the open-ground plots 

 (Series 2) the materials, in the foregoing ratio, were lightly forked into the 

 top three inches of soil. 



For comparative purposes suitable " Controls " were arranged (generally 

 in duplicate). Where Farmyard Manure or Complete Fertiliser was added, 

 the amount applied was such as is usually recommended for good average 

 cultivation. 



Those who possess a knowledge of Radium are aware that the Ores often 

 contain many other chemicals or agents in addition to Radium, and it had been 

 suggested to me on several occasions that these impurities, if I may so term 

 them, might to some degree vitiate the results of these experiments owing to 

 the fact that small quantities of copper sulphide and arsenic are sometimes 

 present. Having secured, in confidence, the analysis of one of the Ores, showing 

 the approximate percentage of impurities it was known to contain, I succeeded 

 in obtaining a sufficient quantity of each impurity, to allow of a prescription 

 being prepared which corresponded as nearly as possible to the original 

 Ore, without of course the Radium. This prescription is referred to as 

 " Chemical Mixture." In this connection I should like to acknowledge my 

 indebtedness to Professor Duffield, B.A., D.Sc., of University College, Reading, 

 for his valuable assistance. I also procured a supply of pure Radium 

 Bromide, which obviously contained no foreign agent that could have an 

 injurious effect upon plant life, and the tests made with it show some 

 extremely interesting results. 



The proprietary radio-active fertilisers named in the list on page 4 were 

 included in these experiments solely for the purpose of obtaining information 

 as to their respective values, and I have no wish to comment favourably or 

 adversely concerning either of them. 



The inclusion of coal dust in the list of dressings is due to the fact that a 

 purchaser of the preparation known as Lignaite is instructed to mix it with 

 coal dust before application, and I was anxious therefore to test the comparative 

 value of coal dust itself. 



