162 FROM NEBULA TO NEBULA 



rotation. This view was blindly adopted by Newton him- 

 self, and is the one universally acquiesced in to-day by all 

 recognized scientists. Some skeptical lay readers may in- 

 fer that the ring, to some extent at least, may be the cum- 

 ulative effect of the long past, but let me assure him 

 solemnly that this is not the orthodox interpretation. In 

 the time of Newton the thickness of this ring at the equa- 

 tor was supposed to be 85,472 Paris feet (a Paris foot be- 

 ing about 1-15 longer than the American standard), but 

 the modern estimate is only 13- J^ miles (71,280 feet). 



By a combined process of pendulum experimenting 

 and computation, Newton arrived at the conclusion that 

 the centrifugal force of the earth's rotation at the equator 

 serves to lighten any given body at that place by 1-28P of 

 the weight it would have were the globe at rest ; that is to 

 say, the centrifugal force there is equal to 1-289 of 

 gravity. Continuing, he reasoned that, inasmuch as this 

 force, being equal to 1-289 of gravity, sufficies to elevate 

 her equatorial regions by 85,472 feet, the attraction of 

 the sun, which is 1-12,868,220 the strength of gravity, 

 should be able to elevate those regions by 289 times 

 85,472 feet, or 24,701,408 feet divided by 12,868,200, or 

 very nearly 2 feet. But let me quote his own words 

 (Book III, Prop. 36, Principia) : 



Cor. Since the centrifugal force of the parts of the earth, 

 arising from the earth's diurnal motion, which is to the force of 

 gravity as I to 289, raises the waters under the equator to a height 

 exceeding that under the poles by 85,472 Paris feet, as above, in 

 prop. 19, the force of the sun, which we have now shewed to be 

 to the force of gravity as i to 12,868,200, and therefore is to that 

 centrifugal force as 289 to 12,868,200, or as I to 44,527, will be 

 able to raise the waters in the places directly under and directly 

 opposed to the sun to a height exceeding that in the places which 

 are 90 degrees removed from the sun only by one Paris foot and 

 11-1/30 inches, for this measure is to the measure of 85,472 feet 

 as I to 44, 



At this stage Newton appears to have rested his case, 

 but not so his successors, who have had the desperate 

 courage to pursue his fatal logic further, even to the 

 bitter extreme of swallowing the inescapable reductio ad 

 dbsurdum that neither the moon or the sun is the dynami- 



