160 FROM NEBULA TO NEBULA 



stronger, tidally, than the sun, instead of 180 times 

 feebler. 



Observation, from Newton's day to this, has failed to 

 reveal any signs of a separate double solar tide, which 

 theory indicates should exist. According to modern com- 

 putations, the ratio of the two tidal forces is, roughly, two 

 to one instead of four to one ; hence the academical argu- 

 ment for the visibility of such a separate solar tide looms 

 stronger to-day than it appeared in Newton 's age. He 

 sought to explain the physical absence of this tide by 

 postulating a merger of the solar with the lunar tide, at 

 one time augmenting and at another offsetting it, ac- 

 cording to the relative angular positions of the two bodies 

 with respect to the earth. 



Now, although it is quite true that there is a startling 

 coincidence between the measure of the daily advance of 

 the moon eastwardly in her orbit and the interval between 

 the arrival of successive high tides at any given port 

 51 minutes in both cases there is a no less startling 

 discrepancy as to the meridianal places of the moon and 

 high tide at any given moment. According to the main 

 hypothesis, high tide should occur immediately under 

 the moon ; for instance, when the moon is on the meridian 

 of New York, high tide should then be filling that city's 

 harbor. Instead, we find that when this latter event 

 occurs the moon has preceded it by about eight hours, 

 and is already some thirty degrees below New York's 

 western horizon ! Why this great hiatus between cause 

 and effect? Newton claims it is due to the "dragging" 

 of the tides, arising from the presence of interposing 

 land masses, friction on the ocean beds, and the inertia of 

 the water itself. 



The assumption that the moon draws the oceans 

 away from the earth's solid part clearly implies a superi- 

 ority in the degree of the intensity of her attraction 

 upon the oceans, as contrasted with her pull on the kernel, 

 and a relative holding back of the latter. Newton knew 

 as certainly, although not so accurately as we, that the 

 density of the earth's solid part is several times greater 

 than that of water and that, by the strict law of mass, the 



