20 FKOM NEBULA TO NEBULA 



Shortly before the middle of the past century the theory 

 of the mechanical equivalent of heat had its birth, and it 

 was then immediately contended that the Nebula must 

 have been cold to start with, but that the kinetic energy 

 developed by the falling together of its component mat- 

 ter into the large bodies of the sun and planets initially 

 heated them in a degree proportional to their respective 

 masses. Mathematicians, however, soon showed that, so 

 far at least as the sun was concerned, the new hypothe- 

 sis was absurdly below requirements ; and this finding it 

 was that evoked the suggestion from Helmholtz that the 

 sun is still a contracting body, that is to say, one in which 

 the energy due to "position" is still in process of conver- 

 sion into kinetic energy. Although this theory was 

 tenaciously adhered to for decades, in spite of its geologi- 

 cal contradictions, it finally succumbed to the joint attack 

 of the mathematician's pencil and the new champion, 

 Radium. But alas, and alas !, according to Doctor S. A. 

 Mitchell (Pop. Astr., June, 1913) : 



From theoretical considerations we are positively convinced 

 that there must be radium in the sun. But to prove this is an- 

 other problem ! With the spectra we already have, we can prove 

 nothing but coincidences. 



In a nutshell, then, the source of the sun's heat is still 

 a wide-open question. 



INDIVIDUAL CHAKACTERISTICS OF THE PLANETS 



Given sound principles of cosmology, scientists 

 ought to be able to deduce from the main facts of the in- 

 dividual case, i. e., the mass of the planet and its solar 

 distance, just what its surface, climatic and other condi- 

 tions must be ; resorting to instrumental observation 

 more as a check than for a solution. That the principles 

 on which they rely are not sound, however, is demon- 

 strated by the controversies now going on between the 

 "Vulcanists" and "Bolidists" as to the character of the 

 moon's surface, and between the "Canalists" and "anti- 

 Canalists" as to the meaning of the Martian lines, etc. 

 Indeed, it will be found difficult to cite a single instance 



