742 Dr. H. Wilde on the Origin of 



which have since presented themselves to me, would be of 

 value in continuation of my papers recently published by 

 the Society *. 



While the principle of" dualism is abundantly manifest in 

 every department of knowledge and fully recognized in the 

 attractions and repulsions in molecular physics, the pheno- 

 mena of the repulsive energy of celestial bodies have so far 

 been unduly obscured by the more general principles of 

 mo vina force and the attraction of gravitation. 



The doctrine that the solar system, as at present consti- 

 tuted, was formed by the successive condensations of a 

 nebular substance rotating about a central position, has been 

 more firmly established during recent years through the 

 great advances made in stellar photography, by which many 

 of the nebulae are visualized in various stages of evolution 

 as right- and left-hande 1 spirals, and clearly indicating the 

 direction of their revolutions t. 



The more interesting of these nebulas are M.31 Andromedse, 

 M.51 Canum, M.100 Comae, M.74 Piscium, and many others 

 from which the origin of planetary systems may be inferred 

 with the same degree of probability as in the historical 

 sequences observable in chemistry, geology, biology, or in 

 any other department of the natural sciences. 



That the subsequent condensations of planetary nebula? 

 into spherical bodies would be attended by the evolution of 

 an amount of heat sufficient to make them vividly incan- 

 descent, is an obvious conclusion drawn directly from ex- 

 perimental science. It will be further evident that, after 

 the heat of compression had attained its maximum, the self- 

 luminous planets would ultimately become dark bodies through 

 the radiation of their heat into free space. 



It is very generally admitted that the sun, notwithstanding 

 his vast dimensions, would, by continuous loss of heat, 

 ultimately become a dark body like each member of the 

 planetary system. It is also known that the internal parts 

 of the sun are in a gaseous condition and under immense 

 pressure. Some idea of the repulsive force exercised by this 

 pressure may be formed from the ejection of enormous 

 masses of incandescent gas from the surface of the sun to 

 the height of 200,000 miles, with an estimated velocity of 

 16b* miles per second J. 



* Manchester Meiroirs, vols. liii. liv. 1909, 1910. Phil. Mag. [G] 

 vols, xviii. xix, 1909, 1910. 



t " Celestial Photographs," by Isaac TCoherts, F.R.S., vols. i. ii. 1893, 

 1899. 



} Young, American Journal of Science, 18/1, p. 468. 



