COSMOGONIES 119 



orbit of Mercury. Further, the several planets do 

 not move at relative rates proportionate to the rate 

 of rotation of the fire-mist at the time of their origin, 

 and this, according to the laws of mechanics, they 

 ought to do. And there are many other facts that 

 have almost completely overthrown belief in the 

 nebular hypothesis as formulated by Laplace, nor 

 have any means been found to patch it up into a 

 consistent and credible theory, though notable 

 attempts have been made by Roche, Kirkwood, 

 Faye, and other physicists. 



Further attempts have been made by M. du 

 Ligondes, Sir Robert Ball, Arrhenius, Chamberlin, 

 Moulton, Lockyer and others to formulate a con- 

 sistent hypothesis, but none of these have been 

 entirely successful. 



The tendency of the more recent hypotheses 

 has been to start with a nebula of low temperature, 

 and, in accordance with thermo-dynamic principles, 

 to derive any necessary heat from the contraction 

 of the nebular constituents under the influence of 

 gravitation. 



Perhaps the most famous of modern theories 

 is the meteoric hypothesis, first proposed by 

 Chadli as far back as 1794, and resuscitated and 

 developed by R. A. Procter in 1870 and by Sir 

 Norman Lockyer in 1887. 



It is a well-known fact that the earth, as she spins 



