358 ANNUAL KEPOKT SMITHSONIAN INSTITUTION, 1908. 



strong as to be equally convincing. Recent work on tlie question of 

 the influence of conditions of extreme pressures and temperatures on 

 the radio-active properties of radium appear to show that, as would 

 be anticipated, the effect is small, if indeed existent. As observed by 

 Makower and Rutherford, the small diminution noticed under very 

 extreme conditions in the y radiation possibly admits of explanation 

 on indirect effects. These observations appear to leave us a free hand 

 as regards radio-thermal effects, unless when we pursue speculations 

 into the remoter depths of the earth, and even there, while they remain 

 as a reservation, they by no means forbid us to go on. 



The precise quantity of heat to which radium gives rise, or, rather, 

 which its presence entails, can not be said to be known to within a 

 small percentage, for the thermal equivalent of the radio-active energy 

 of uranium, actinium, and ionium, and of those members of the ra- 

 dium family which are slow in changing, has not been measured 

 directly. Professor Rutherford has supplied me, however, with the 

 calculated amount of the aggregate heat energy liberated per second 

 by all these bodies. In the applications to which I shall presently 

 have to refer I take his estimate of 5.6X10""- calories per second as the 

 constant of heat production attending the presence of one gram of 

 elemental radium. 



To these words of introduction I have to add the remark, perhaps 

 obvious, that the full and ultimate analysis of the many geological 

 questions arising out of the presence of radium in the earth's surface 

 materials will require to be founded upon a broader basis than is 

 afforded by even a few hundred exj^eriments. The whole sequence of 

 sediments has to be systematically examined; the various classes of 

 igneous materials, more especially the successive ejecta of volcanoes, 

 fully investigated. The conditions of entry of uranium into the 

 oceanic deposits has to be studied, and observations on sea water and 

 deep-sea sediments multiplied. All this work is for the future; as 

 yet but little has been accomplished. 



THE ItADIUM IN THE ROCKS AND IN THE OCEAN. 



The fact, first established by Strutt, that the radium distributed 

 through the rock materials of the earth's surface greatly exceeds any 

 permissible estimate of its internal radio-activity has not as yet re- 

 ceived any explanation. It might indeed be truly said that the con- 

 centration of the heaviest element known to us (uranium) at the sur- 

 face of the earth is just what we should not have expected. Yet a sim- 

 ple enough explanation may be at hand in the heat-producing capacity 

 of that substance. If it was originally scattered through the earth- 

 stuff, not in a uniform distribution but to some extent concentrated 

 fortuitously in a manner depending on the origin of terrestrial ingrc- 



