198 



Dr. C. Ohree on Applications of Physics 

 Numerical Results : Lunar Influence. 



80 X 10 7 grammes wt. 

 per sq. cm. 



11 X 10 7 grammes wt. 

 per sq. cm. 



2gpa\Vdn = 



35/76 



700/209 



1 : l-\-2f/pa/l9?i (approx.) = 



11 :16 



3:13 



u a = 



^ 3 cos 2 0-1 



28 q cms - 



co 3 cos 2 0-1 



68 ~ cms. 



V a = 



— 2 . 6 cos 6 cms. 



—61 sin 9 cos 9 cms. 



Polar less equatorial radius = 



cms. 



102 cms. 



Apparent change level, &// = 



0"-; ^sin 20 



O"-OO4sin20 



Apparent change of star's 1 _ 

 altitude, 8a \ 



0"-02i sin 26 



0"*027 sin 29 



The reduction effected by the self-gravitational forces in 

 Thomson and Tait's estimate, O^Ol? sin 26, for the apparent 

 change of level increases conspicuously" as the rigidity 

 diminishes. In fact, for the lower value of n, o^ would 

 be iusensible unless with an instrument recording to -gJ-^ of a 

 second of arc. 



On the other hand, the changes in the shape of the earth 

 and in the star's apparent altitude are very decidedly larger 

 for the lower value of n. 



Corresponding results of about half the numerical size of 

 the above would be obtained in the case of solar influence. 



Final Conclusions. 



§ 32. The results obtained indicate at least the directions in 

 which luni- solar effects may be profitably looked for. If the 

 earth's elasticity for luni-solar influence be perfect, apparent 

 changes of level or star's altitude will be nil when the moon 

 or sun, as the case may be, is either in the zenith or on the 

 horizou, while they will be a maximum when the altitude 

 is 45°. If the elasticity be not perfect, a lag in the tides may 

 be expected. As regards star's altitude, a hopeful feature is 

 that the influence, being the same for all stars in the same 

 vertical, should be easily separable from terrestrial refraction. 

 The further fact that the apparent change is proportional to 

 the cosine of the star's azimuth measured from the vertical 

 plane containing the moon, or sun, may prove of assistance. 



It would appear that luni-solar effects are not unlikely to 

 prove of as much consequence as the direct pressure or 

 gravitational effects of any ordinary differential meteorolo- 



