110 FROM NEBULA TO NEBULA 



ence over all other theoretical problems. The one great, 

 obsessing aim has steadily remained, not to accept it as 

 a friendly guide-post to new truth, but as an obstruction 

 in the road which must be calculated out of existence at 

 any cost. Fortunately for the salvation of the science, it 

 is now all but universally conceded that "this deviation 

 of the moon from its calculated path cannot be accounted 

 for by any gravitational cause" (i. e., consistently with 

 Newtonian theory) and numerous conjectures are being 

 improvised to account for it on its own merits; none of 

 which, however, possess any correlating virtues. Doctor 

 See, for example, claims to explain it by postulating a 

 "gravitational, screening effect " by the periodical eclip- 

 sing of the moon by the earth, and vice versa; thus ob- 

 viously not only cutting this phenomenon off from all pos- 

 sible relation to others, like the anomaly of Mercury and 

 the rotation of the apsides, but dangerously impugning 

 the law of mass by implying a similar screening of the 

 rear hemisphere of every planet by its fellow. 



Had astronomers been as slovenly in their character 

 as mathematicians as they have been in their character 

 as theorists, this delicate deviation in the lunar motion 

 would long since have been brushed aside and forgotten. 

 For, as theorists, they have admitted terms which should 

 have been excluded, while as mathematicians they have 

 taken the utmost pains to incorporate even the most in- 

 significant of genuine factors. The worst offender of all 

 was Laplace, who in excess of zeal introduced the eccen- 

 tricity of the earth's orbit as a cause, when under any 

 view of the case, whether Newtonian or mine, this eccen- 

 tricity should properly be treated as a concomitant effect 

 of the underlying dynamical agencies at work, whether 

 these latter be known, or simply inferred. As for the 

 amazing and highly creditable care exercised by the 

 mathematicians, let these extracts show: 



Notwithstanding the accuracy of Mayer's tables, an irregu- 

 larity had been discovered by observation which was not indicated 

 by the theory of gravity. Halley and other astronomers had 

 placed it beyond a doubt that the moon performed her monthly 

 revolutions round the earth in a shorter time than formerly. 



