Cliase.] ^ i ^ [Nov. 4, 



93. Internal Energy of Ice. 



According to the kinetic theory of gases, the internal movements of the 

 particles of steam are rectilinear, representing a total vis «ica of projection, 

 against the uniform resistance of gravity, of about | X 1389.6 d feet = 

 189.43 miles. While the steam is condensed in the form of water or ice, 

 the internal energies tend to maintain a spherical figure. The resultant 

 oscillations (Note 23), can therefore be represented by a conical pendu- 

 lum of \ the height of total projection, or ^ of the projectile vis viva of 

 evaporation. This gives, for the virtual fall from incipient ebullition to 

 total congelation, A^ = i A == 47.355 miles == 250033 feet ; and for the 

 heat of sphericity ^j = a <? =^ 179^.931 C. Deducting 100^ for the expan- 

 sion from the freezing to the boiling point, we have 79^.931 for the "latent 

 heat " of ice, or the heat which is required to overcome its internal energy. 

 The following values have been deduced experimentally : 

 Desains and De la Provostaye 79°. 25 



Black ' 790.44 



Person SO^.OO 



Hess 800.34 



94. Photodynandc Moment of Inertia. 



Much of the difficulty which has been encountered in trying to recon- 

 cile the nebular hj-pothesis with actual planetary arrangements, has arisen 

 from overlooking the difference between nucleal retardation and free 

 orbital revolution. Herschel's doctrine of "subsidence" removes this 

 difficulty, and an examination of the primitive planetary belt, before any 

 of its successive divisions into asteroidal and intra-asteroidal belts, two- 

 planet belts, and single-planet belts, shows the photodynamic influence 

 in a very striking manner. The limit of photodynamic nucleal rotation is 

 in the asteroidal belt ; the photodynamic limit of "subsidence " rotation is 

 at the solar modulus of light. I have often shown* that Saturn represents 

 the photodynamic centre of inertial moment ; in the division of inertia 

 among the several belts, provision has been made for the change of 

 linear into synchronous conical oscillations (4:1); for the change of 



3 

 synchronous into orbital oscillations {t oz P) ; for the ratio of nebular 



radii to radii of subsidence-collision (f) ; and for the relative variability 

 of centripetal and orbital tendencies, {g cc i\^). Hence we find 



4^ X (!)* X i/o : «?6 : : n : v. 

 Substituting the values of Y^ and v^ (Note 92) we get 



1/^ = 3502.2 Wig. 

 Bessel's estimate was 3501.6. 



95. Photodynamic Centres of Gravity. 

 An interesting approximation is shown by the ratio 



33 X 5 X i^o : ^h : : K : «3- 

 * Note 12 ; ante, xviii, 431 ; et al. 



