Chase.] 



364 



[April 15, 



The second term of this proportion represents Callisto's semi axis major ; 

 the third term, the velocity of light ; the fourth term, the velocity acquired 

 by infinite fall to Sun's surface. 



V. The pendulam-factor, 3, appears in the Jovian system, in a primitive 

 radius =-. 3* X 1.433 = 38.424 semi-diameters, 1.423 being the theoretical 

 ratio of the radius of constant volume to the radius of constant pressure.* 



The following table shows the influence of harmonic vibrations upon the 

 positions of Jupiter's satellites. The harmonic divisor for Callisto is 

 very nearly 1 -f- 2 ay the other theoretical divisors have a constant third 

 difference of a. 



Observed 



30. The Moons of Saturn. 

 The photodynamic centre of planetary inertia presents the following 

 evidences of the influences of sethereal undulation : 



I. Titan, Saturn's giant moon, bears witness to the rupturing tendencies 

 at the centres of nebulosity and of planetary inertia, in the proportion : 



Saturn's secular perihelion : Jupiter's mean perihelion : : Titan's semi- 

 axis major : Sun's semi-diameter. 



8.7344 : 4.9783 : : .00817 : .00466. 



II. The combined influences of orbital revolution at the centre of density, 

 and of Laplace's tendencies to synchronism, are shown in the approximate 

 equivalence of the terrestrial year to 23 orbital revolutions of Titan. 



366.2565 = 23 X 15.934 ; Titan's orbital period = 15.945 days. 

 *Proc. Am. Phil. Soc. xiv, 651. 



