RADIOACTIVITY A FACTOR OF PLANT ENVIRONMENT 3 1 



Carbon-dioxide from great depths of old volcanic soil was markedly 

 radioactive, and Sarasin ^''^' ^''^ demonstrated the same property in air 

 from the so-called "breathing wells" in Europe. The radioactive 

 gas in the air and soil of New Haven (Connecticut, U. S. A.) was 

 determined by Bumstead and Wheeler^^ to be identical with the 

 emanation of radium. McLennan^^ also found that natural gas 

 from wells in the Welland district, near Niagara Falls, and near 

 Brantford, was charged with a radioactive emanation, and in the 

 experiments of Dadourian^^ the activity of underground air was found 

 to be due to thorium. A radioactive emanation, evolved on heating 

 raw petroleum, is considered by Burton ^^ to be due solely to the 

 presence of radium in the soil. 



The General Distribution of Radioactivity : Evidence 

 from the general distribution of radioactive substances, that radio- 

 activity is a factor in the normal environment of plants has been 

 shown to be abundant. Numerous other researches give added em- 

 phasis to this fact. The discharge of positive electrification by 

 metals at a temperature of 270° C, or over, ^^'*^' ^^'"^ the evidence that 

 the photosphere of the sun is emitting electrons in large quantities, ^^ 

 which travel throughout the solar system, the probable existence of 

 electrons in metals at all temperatures moving freely between the 

 molecules, ^^ and causing a " soft" X ray when they collide with the 

 molecules, are all facts pointing to the same conclusion. 



Drops of spray on striking wet rocks at the foot of water-falls 

 communicate a positive charge to the water and a negative charge 

 to the air.^*^ A very penetrating radiation has been found to exist 

 inside buildings, ^^'^^ and zinc and tinfoil, lead, copper, glass coated 

 with phosphoric acid, silver, copper, platinum, aluminium,"^ dried 

 earth, polished tin, brick, iron,^" and hydrogen-peroxide,^'' have all 

 been found to be radioactive, most of these substances giving off rays 

 comparable to the /9 rays of radium. Experiments of McLennan 

 and Burton^* indicate that all metals in varying degree are sources 

 of marked, though feeble, radioactivity, and that " the ordinary air of 

 rooms is traversed by an exceedingly penetrating radiation," such as 

 comes from thorium, radium, and the excited radioactivity produced 

 by them. Campbell, ^^' -^ after testing nine different metals, all of 

 which are included in the lists given above, states that '* the emission 

 of ionizing radiation is an inherent property of all the metals investi- 

 gated," and adds, *' I see no reason why it should not be extended to 



