Chase.] ^55 [April 15, 



semi-axis major by Sun's semi-diameter, we could easily compute Sun's 

 mass and distance. Different observers give measurements of Sun's diame- 

 ter, -wliich vary through a range of about a fourth of one per cent. 



In expanding or condensing nebulae, I have shown that Laplace's limiting 

 or atmospheric radius varies as the | power of the nucleal radius. Onr first 

 step towards transforming Earth's orbital into nucleal efficient velocity, is 



gt 4 



to multiply ^ X (1 + e)''- by (1 + ey. We must also multiply by tt, 



because the time of acquiring the efficient velocity is tt times as great as 

 the time of acquiring orbital velocity, and by n*, because Sun's equatorial 

 velocity of rotation is n times as great as the corresponding velocity of rota- 

 tion when expanded to Earth's orbit. We then have : 



Earth's -^ X (1 + e)^ X {1 -\- e)i y^ r. n ~ velocity of light = 10089.15 



X 270.68 H- n^. 

 The right-hand member of this double equation is obtained as follows : 

 If ^ = Earth's semi-axis major, its orbital velocity is 2 :r ^ -^- 31558149 ; 



the velocity of light being p h- 497.827. But 270.68 is n^ times Earth's or- 



/ 31558149 \ 



bital velocity ; therefore, the velocity of light is l o ^ v 4Q7 8'>7 ^^ 10089.15 I 



X 270.68 -^ n^. 

 Solving the equation, we find : n =214.4775; v^ = 186,385.7; p = 



497.827 ., == 92,787,850 miles; ra, = {^^' -h (goT^fW)' = 

 381,799 mi. 



This purely photodynamic determination of p differs by less than -^^ 

 of one per cent, from the partially thermodynamic determination in the 

 foregoing note. 



18. Nucleal and Rupturing Centres of Condensation. 



Our next tentative step is to Venus, the nearest and brightest of Earth's 

 sister planets, and the only one which shares with Earth the peculiarity of 

 sometimes having an orbit, in the course of its secular changes of excen- 

 tricity, which is entirely circular. This fact, together with Earth's central 

 position in the dense belt, indicates a purely nucleal origin for that belt ; 

 the other planets showing more obvious evidences of an origin which was 

 partly atmospheric, and of the influences of "subsidence" which were 

 so happily pointed out by Herschel. The nascent vis viva of Venus, 



{gtV 



\2i a was also a rupturing vis viva in the dense belt, as is shown by the 



following relation between Earth's semi-axis major, p^, and Venus's secular 

 perihelion radius-vector, p . 



\%}a •\2)fi • • P^ -Pp ^^■■> 



*n represents the quotient of Earth's semi-axis major by Sun's semi -diameter. 



