160 FKOM NEBULA TO NEBULA 



though the latter is some eight hours in her wake, ex- 

 hibit such a singular correspondence in their schedules? 



To begin with, I urge upon you, as an honest jury- 

 man, not to ignore the moon's sound alibi. She has 

 never yet been discovered in flagrante delicto. Count- 

 less human eyes, including Darwin's, can testify that at 

 the time she is accused of having lifted the tide in the 

 mid- Atlantic, she wasn't there at all, but mid-over the 

 Pacific. She is the victim of incriminating circum- 

 stances, perhaps, but she is immaculately innocent. 

 Darwin, you know, accused her even of repelling the seas 

 under her, for which he had better cause; but in the end 

 he preferred to believe her guilty of the crime alleged, in 

 shameful disregard of the evidence. 



The whole mystery dissolves away with the discov- 

 ery of the true tidal cause. Without being able to 

 fathom the physical reason, astronomers have discovered 

 that changes of momentum in this or that member of 

 a cosmic system, whether orbital or axial, are invariably 

 compensated by reverse changes elsewhere. They call 

 this "the law of conservation of moment of momentum ". 

 With them it is only an empirical fact, an arbitrary pro- 

 vision of Nature's, dictated neither by discoverable rea- 

 son or necessity. 



Our present inquiry as to why the moon and the tidal 

 crest keep pace, affords us an excellent opportunity to 

 emphasize and illustrate the advantage of the principle 

 of equilibrium over the denial of it as a key to the struc- 

 ture of the cosmos, and to point out the superiority of 

 physical causation over cryptic abstractions. The 

 studious reader who has done me the honor to read thus 

 far must now be as familiar as myself with the concep- 

 tion of what a "gravitational unit" is, and how our bi- 

 nary earth-moon system maintains its balance, progres- 

 sively, in the face of all adverse outside attractions. 

 One the chief disturber of this equilibrium is, of 

 course, the sun. By virtue of his differential attraction 

 upon the kernel of the earth and her seas, the planet is 

 obliged to redispose her mobile parts to wit, her oceans 

 in such a way as not only to trim her own balance, but 



