56 Kansas Academy of Science. 



THE MODULUS OF LUNAR INFLUENCE, NOT IN A 

 LIFTING, BUT IN A FALLING MOVEMENT. 



By J. J. Jewett, Sawtelle, Cal. 



IN the opinion of the writer, there is a general misconception of 

 the immediate cause of the phenomena of the semidiurnal 

 oceanic tides. I approach the subject very directly, that its discus- 

 sion may not extend this paper beyond proper limits. 



The usual explanation of the modus operandi of the moon's in- 

 fluence is very unsatisfactory to the ordinary inquirer, and espe- 

 cially that part of it which attempts to account for the tidal flow 

 opposite the prolunar side of the earth. Perhaps the failure of the 

 scientific expositors is due to a mistaken impression of how the 

 moon's power is applied. The most important vantage is discarded 

 or neglected. The pulling of the moon upon the waters of the pro- 

 lunar geohemisphere is assumed to be the main cause of the tidal 

 wave on that side of the earth, the sun coming in as an adjunctive 

 or diversive agency, as the case may be. On the opposite hemi- 

 spere the marine proturbance results from the unequal pull on the 

 ocean bottom and the ocean surface, or, as some express it, by a 

 pulling away of the land from the waters, "as it were," as a quali- 

 fying phrase, which, to use another metaphor, is putting the propo- 

 sition into a ruminant's paunch for subsequent mastication. It is 

 difficult to conceive the power thus attributed to the moon as really 

 operative, while our senses give no indication of it in our physio- 

 logical experience. It is still more difficult for the student to men- 

 tally perceive how the land and sea are pulled apart on both sides 

 of the globe simultaneously. 



I will endeavor to show a cause of tides more powerful than the 

 moon's direct action, and the operation of which can be more 

 easily comprehended, existing within the compass of the earth, and 

 subject to the laws of gravity. The tendency of concrete bodies 

 to approach each other is proportioned to the sum of their masses, 

 modified by the spatial degrees of separation, diminishing as the 

 latter increases, and augmenting as it declines in proportion to the 

 square of any lineal unit or units of measure. That is to say, if 

 their distance apart is doubled, the gravitational force is reduced 

 to one-fourth its previous power ; but if the original distance is re- 

 duced to one-half, the power is increased fourfold. Now, in 

 spheres, if the mass is distributed symmetrically, the center of 



