288 BECKER AND DAY 



To what extent detailed observations will show a history of 

 this kind for ore deposits, it is too early to say, but it is cer- 

 tainly worth while to draw the attention of geologists and min- 

 ing engineers to the possibilities thus presented, and to dynamic 

 conditions which may prove important as well as interesting. 



To the physicist also the phenomena cannot be uninteresting. 

 The power which roots exhibit to prize apart large building 

 stones we are content to classify as "vital" and mysterious. 

 We cannot so easily dispose of the similarly intense force with 

 which, as it appears, inorganic molecules drive themselves into 

 place, much as oakum is driven into the seams of a ship by a 

 caulking iron. We hope to be able to continue this study at 

 some future time. 



