Mat 14, 1915] 



SCIENCE 



733 



3,520 years, to J in 5,280 years, and so on. 

 Thus the total energy ultimately evolved from 

 1 pound of radium is equivalent to more than 

 70,000 twenty-four-hour days of horse-power. 



Many experiments have been made to ascer- 

 tain the effect of radio-activity on plant 

 growth; and in general a distinct influence is 

 noted, although some experimenters report 

 negative results. 



Gager'- in summarizing his investigations 

 states that radium acts under certain condi- 

 tions as a stimulus to physiological processes, 

 but, if used in too great strength or for too 

 long a period, it may retard development or 

 even kill the plant. 



Fabre^ noted some beneficial effects from 

 emanations, using a concentration of IJ micro- 

 curies^ for each 2 liters of air, but injury from 

 greater strength. 



Stoklasa* found that radium emanations 

 promoted germination of seeds and accelerated 

 the growth of plants to a considerable extent. 

 From earlier experiments he has reported in- 

 creased fixation of nitrogen by bacteria. 



In the spring of 1913, through the kindness 

 of the Standard Chemical Company of Pitts- 

 burgh the University of Illinois Agricultural 

 Experiment Station was enabled to begin a 

 series of field experiments with radium as a 

 fertilizer or crop stimulant. The company was 

 deeply interested in having the experiments 

 conducted, and the radium salts furnished to 

 us were prepared under the direction of Doctor 

 Otto Brill and Doctor Charles H. Viol, of the 

 radium research laboratory of the Standard 

 Chemical Company, the quality and strength 

 of the preparations being thus assured. 



The value of radium is about $100 per miUi- 

 gram and in order that the field investigation 

 might have a direct relation to practical agri- 



^ Popular Science MontMy, Vol. 74, pp. 222-32. 



2 Compt. Send. Soo. Biol., 70, 187, 419. 



3 A microeurie is a millionth part of a curie, the 

 unit of measurement for radio-activity, which is the 

 quantity of radium emanation in equilibrium with 

 one gram of radium. In other words, the curie 

 represents the constant or continuous energy of one 

 gram of radium. 



iChemilcer Zeitung, Vol. 38 (1914), No. 79, pp. 

 841-44. 



culture, the radium was used at three rates of 

 application, costing, respectively, $1, $10 and 

 $100 per acre ; or in amounts of .01 milligram, 

 .1 milligram and 1 milligram of radium per 

 acre. If the effect of the application should 

 be marked and permanent, even the initial 

 expense of $100 per acre might be desirable. 



The fields selected for these experiments were 

 the north division of Series 200 and the south 

 division of Series 600 of the agronomy plots on 

 the South Farm of the University of Illinois. 

 Each of these fields includes 144 fortieth-acre 

 plots, two rods square, besides some divisions 

 and border strips, making the field sixteen rods 

 wide east and west, and thirty-eight rods long 

 north and south. 



On Series 200 and on the west part of Series 

 600, the radium was applied in a solution of 

 radium barium chloride diluted with dis- 

 tilled water, the check plots receiving the same 

 quantity of distilled water without radium. 

 On the east part of Series 600 solid radium 

 barium suKates were applied, after diluting 

 by thoroughly mixing and pulverizing with dry 

 soil from the field, the check plot receiving the 

 same weight of soil without radium. The pul- 

 verized soil was applied with a force-feed grain 

 drill, and the solutions with an Aspinwall 

 barrel sprayer. 



The amount of radio-active substances ap- 

 plied in these tests was purposely made small, 

 in order to avoid any appreciable effect of the 

 substance other than that due to radio-activity. 

 It is conceivable that some effect might be ob- 

 tained from the application of 100 or 200 

 pounds per acre of mineral salts. The amount 

 in the case of the heaviest applications was less 

 than five pound of total salts per acre. 



On both fields corn was grown in 1913 and 

 soy beans in 1914. Owing to other experi- 

 mental work involving some variations in 

 planting, only part of Series 600 furnished 

 comparable data in 1913, only twenty-four 

 separate trials being provided. The work of 

 the two years,"* however, comprised 144 tests 

 with corn and 240 tests with soy beans. Aside 



5 For detailed data see Bulletin No. 177, Uni- 

 versity of Illinois Agricultural Experiment Sta- 

 tion. 



