14 I 1 'BOM NEBULA TO NEBULA 



its primordial state? If this be so, as soon as matter changes 

 from this state to another in which gravity [i. e. centripetal at- 

 traction] begins to act, or to act freely, motion [i. e. centrifugali- 

 zation]will arise, and it is evident, that, as a rule, the motion 

 must be accelerated, at least during immense periods, so that the 

 longer the period elapsed since the birth of the stars the greater 

 must be their average velocity. 



THE LAW AND PRINCIPLE or GRAVITATION 



Scientific students have become so accustomed to 

 the idea of gravitation acting as a bond between cosmic 

 bodies that they appear to have lost sight of the fact that, 

 after all, it is essentially only an hypothesis, and that 

 therefore its demonstration must be unequivocal and pre- 

 cise, or, as the lawyers say, beyond a reasonable doubt. 

 Newton recognized this clearly, as was evidenced by his 

 laying aside his earlier computations because of a con- 

 flict between the then existing data and the result he 

 sought to prove. By a piece of rare good fortune the 

 fatal error was subsequently corrected by others, and on 

 making a second trial the new term was found to fit the 

 case. 



Now, there exist to-day two just such discrepancies 

 between the observed and the computed places of bodies 

 in our system which haunt the mathematical astronomer. 

 The first is known as the anomaly of Mercury's peri- 

 helion movement, and the other as the secular accelera- 

 tion of the moon's mean motion. There have been 

 numerous attempts made to solve these irregularities by 

 more and more exhaustive analyses, with the ever- 

 present purpose of wiping them out of existence; but to 

 no avail. As blots on Newtonian theory they are 

 indelible. A few more-recent attempts have been made 

 to explain them away as actualities, but equally without 

 success. In the meantime the law of the inverse square 

 stands gravely impugned. Empiricism is not science. 

 But to quote the testimony of the Newtonians them- 

 selves: The first excerpt is from Young (G. A. p. 301) : 



There remains one lunar irregularity among the multitude of 

 lesser ones, which is of great interest theoretically, and is still a 



