372 



KNOWLEDGE. 



October, 1913. 



theoretical doubt that there are tides of the litho- 

 sphere." 



Since then Professor A. Young's discovery of lunar- 

 tide effects on the Karoo has since been published. 

 (" Tidal Phenomena at Inland Boreholes near 

 Cradock," Trans. Roy. Soc. of South Africa. 1913, 

 Vol. Ill, Part I.) 



Moulton : — " In a word, the quantitative results 

 obtained in this paper are on the whole strongly 

 adverse to the theory that the Earth and Moon have 

 developed by fission from an original mass, and that 

 tidal friction has been an important factor in their 

 evolution. Indeed, they are so uniformly contra- 

 dictory to its implications as to bring it into serious 

 question, if not to compel us to cease to consider it 

 as even a possibility." (Page 133.) 



"... The hypothesis of Laplace has the 

 support of no observational evidence. On the 

 contrary, there are well-known considerations . . . 

 which compel us to reject it . . ." (page 137). 

 As to the possibility of the fission-theory of the 

 formation of satellites, planets and double-stars, 

 Moulton's conclusions are : — 



"(1) We find that the Sun cannot arrive at this 

 critical stage (fission) until its mean density shall 

 have exceeded 307 x 10 11 on the water standard. 

 This corresponds to an equatorial diameter of the Sun 

 of about twenty-two miles. 



(2) We find that the Sun cannot become so oblate 

 as Saturn is now until its mean density shall have 

 exceeded 148 x 10 10 on the water standard. . . . 

 Since even the latter density is impossibly great we 

 conclude that the Sun will never become so oblate 

 as Saturn is now, and that it will always be more 

 stable than Saturn is now. 



"(3) We find that Saturn cannot arrive at the 

 critical state at which Jacobian ellipsoids branch 

 until its mean density shall have become twenty-one 

 times that of water. . . We conclude because of the 

 great density demanded that Saturn will never suffer 

 fission." (Page 159.) " Perhaps the hypothesis that 

 stars are simply condensed nebulae, which has been 

 stimulated by a century of belief in the Laplacian 

 theory, should now be accepted with greater reserve 

 than formerly. Up to the present we have made it 

 the basis not only for work in dynamical cosmogony, 

 but also in classifying the stars. It may be the 

 time is ripe for a serious attempt to see if the 

 opposite hypothesis of the disintegration of matter — 

 because of the enormous sub-atomic energies, which 

 perhaps are released in the extremes of temperature 

 and pressure existing in the interior of suns, and of its 

 dispersion in space along coronal streamers or other- 

 wise — cannot be made to satisfy equally well-known 

 phenomena. The existence of such a definitely 

 formulated hypothesis would have a very salutary 

 effect in the interpretation of the results of astrono- 

 mical observations. We should then more readily 

 reach what is probably a more nearly correct 

 conclusion, viz., that both aggregation and dispersion 

 of matter under certain conditions are important 

 modes of evolution, and that possibly together they 



lead in some way to approximate cycles of an extent in 

 time and space so far not contemplated." (Page 160.) 

 Lunn. — "Geophysical Theory Under the Planetesi- 

 mal Hypothesis." 

 In this paper, if I grasp aright the meaning, the 

 author shows, by adopting plausible laws of com- 

 pression and density, that it is only small bodies that 

 can be very dense, which is borne out so far as they 

 go by astronomical observations ; thus we have 



* Uncertain, Stebbins gives Mass 0-55, Density 00.2. 



Cox.—" Beyond the Atom," 1913. 



" One pound of the emanation would, at its 

 maximum intensity, radiate energy at the rate of 

 about ten thousand horse - power. This large 

 emission of energy from the radio-active bodies 

 throws an interesting light on two questions which 

 have long been the subject of controversy, the age 

 of the Earth and the source of the heat of the Sun." 

 (Page 109.) 



Period of fall of Uranium to half-value six 

 thousand million years. (Table, p. 91.) 

 Kelvin (and Green). — " The Problem of a Spherical 

 Gaseous Nebula." Trans. R. S. of Bdin., 1907- 8. 



" It is scarcely possible to conceive that any fluid 

 composed of the chemical elements known to us, 

 could be gaseous in the Sun's atmosphere at depths 

 exceeding one hundred kilometres." (Page 268.) 



Kelvin calls a gas in which a the ratio of the 

 specific heats is greater than 1$ a gas of species P ; 

 and it is almost certain that all monatomic gases 

 have a = If. 



" We see that the central temperature of a globe 

 of gas P in equilibrium increases through gradual 

 loss of heat by radiation into space. We then see 

 also that the internal energy of a globe of gas P, 

 continuing in a condition of approximate equilibrium 

 while heat is being radiated away across its boundary, 

 would go on increasing, and the work done by 

 mutual gravitation of its parts would go on increas- 

 ing till the gas in the central regions becomes too 

 dense to obey Boyle's Law." (Page 281.) 



In this statement no account is taken of any 

 possible liberation of atomic energy, but, even with- 

 out this, it is evident that the underlying idea of 

 contraction is at fault, and that a decrease of 

 internal temperature and increase of size could go on 

 together. So far as observation goes, the evidence 

 is in favour of the latter view. Although hardly 

 supplying an exact parallel, it is well known that the 

 gaseous envelopes of comets contract as they 

 approach the Sun, 



