SYMPOSIUM OX RADIOACTIVITY. 75 



radioactive atoms. It is not improbable that the liquid threads 

 were thus aided in a very special way in boring upward, for it 

 seems obvious that the part of the liquid which carried most of 

 the self-heating constituent would come to have the highest tem- 

 perature, the lowest specific gravity, and the largest gaseous fac- 

 tor — for the disintegration produced gas emanation and helium 

 in addition to the gases generated by the heat alone — and would 

 hence take the uppermost position and bring its liquefying influ- 

 ences to bear on the solid matter which lay between it and the 

 surface toward which it was pressed. The very mechanism may 

 thus have kept the most effective part at the point most critical to 

 its ascent. 



While this outline falls far short of an adequate discussion of 

 the relations of radioactivity to the planetesimal hypothesis, it will 

 perhaps suffice to point out the line of co-operation of the new 

 thermal agency with the new genetic hypothesis. The two seem 

 to co-operate happily. Jointly they seem to furnish a promising 

 basis for a revised thermal geology in harmony with accumu- 

 lating geologic data in various lines and with the growing evidence 

 of the elastic rigidity- of the earth body as a whole. At least the 

 concentration of the radioactive substances at the surface seems 

 to be aptly explained, and the mechanism that conserves the solid- 

 ity of the earth falls into consonance with the new experimental 

 evidence of an elastico-rigid body-tide which seems scarcely less 

 than decisive. 



V. THE BIOLOGICAL EFFECTS OF RADIUM. 



By William Allex Pusey, 



L'niversit}' of Illinois. 



Among the first discoveries made after the production of con- 

 centrated radium salts was that radium is capable of causing 

 intense effects upon living tissues. We were not unprepared for 

 such a discovery in the case of radium, because similar phenomena 

 had been observed early in the study of X-rays. In the case of 

 X-rays the discovery had been totally, and very unfortunately, 

 unexpected. The early burns from radium were of the same 

 character as X-rays burns, and later detailed study has shown 

 that the effects upon tissues of the two agents are practically 

 identical. An appreciation of this fact is useful at the outset of 

 a consideration of the biological effects of radium; it gives one at 



