October. 1911. 



KNOWLEDGE. 



381 



evolution and worthy of the most careful and 

 detailed study on the part of astronomers. 



The diagram. Figure 11, page 382, taken from 

 "The Birth of Worlds and S}stems " was drawn to 

 show the distribution of material at the moment 

 when the three bodies are parting company. Assum- 

 ing the similar suns to be of average dimensions, 

 we can imagine the valleys which have been cut 

 along the equators of the two torn suns to be 

 perhaps something like a million miles in length. 

 The valle\- commences with a mere scraping away of 

 the atmosphere ; it 

 then becomes 

 deeper and deeper, 

 until it reaches far 

 down into the sun. 

 The material is 

 dragged forward, 

 and at the moment 

 of parting with the 

 new third star, it 

 is heaped up into 

 a huge mountain 

 of fire, hundreds 

 of thousands of 

 miles high. This 

 material being car- 

 ried hv momentum 

 in the direction 

 in which it has 

 been dragged, tends 

 to foil o w t h e 

 third star, and so 

 produces rotation 

 in the general 

 plane of the orbits 

 of the two stars. In all probability before the 

 impact occurred the star had a rotation of its own, 

 and hence, immediatelv after the impact, a tumult 

 of conflicting motions of the most extraordinary 

 character must ensue. There is first this struggle of 

 the two rotations, the original and the impressed 

 rotations, that must result in a most extraordinarily 

 irregular rh\thm. Then, again, we have gravitation 

 exerting itself, struggling to make the highly-distorted 

 body into a sphere. We have to remember that not 

 merely is there the enormous disturbance in the form 

 of the torn sun due to the impact itself, but there is 

 the disturbance due to tidal action, and although it 

 is possible that Chamberlain and Moulton greatly 

 exaggerated this action, still tidal deformation must 

 be of a stupendous character. Hence we have 

 gravity struggling to make this ill-formed mass into 

 a sphere. A tremendous inertia of motion will be 

 set up whose momentum must carry the material 

 past the position of equilibrium, and thus another 

 amazingly irregular tidal action must be at work in 

 each of the two torn suns. 



This heated mountainous mass must produce con- 

 vection currents of ordinary gas and volatilized metals, 

 and when this is projected, as it must be, in many 

 cases, for hundreds of thousands of miles above the 



surface of the star, in certain positions this must 

 produce bright line spectra. Especially will such 

 spectra be crossed by the bright line of hydrogen, 

 and this deduction has been conclusiveh' borne out. 

 In fact, not merely are these stars known to be thus 

 characterised, but hundreds of them have actually 

 been discovered by especial search directed to the 



finding of such bright lines. 



Amongst the variables 



Fir.rRi: 10. The Nebula about N'ov 

 Observatorv bv G. W. Ric 



SO discovered, some have proved to be doubly 

 variable double stars : that is to say. double 

 stars that have been so recently wedded by 



attraction of the 

 third bod\- that 

 t he\' may be actually 

 considered to be on 

 their honeymoon. 



It will easily be 

 perceived that all 

 the struggles of 

 motion and the 

 changes in the 

 margins of these 

 vast volcanoes must 

 alter in the most 

 extraordinary de- 

 gree the intensity 

 of luminosit\' at the 

 period of maximum. 

 It must even alter 

 to some extent the 

 time of the appar- 

 ent maximum itself. 

 It might be 

 thought that this 

 complex series of 

 motions, as well as 

 conduction and convection, would rapidly bring 

 about a condition of equilibrium : hence that this 

 inequality of heat of the rotating star would not 

 last long. 



A detailed stud\" into all the conditions that 

 presented themselves was made in 1879, and it was 

 shown that a great number of the agencies tending 

 to equalit\" balanced one another and became 

 ineffective. Hence it appeared at that time — and 

 the opinion has not altered since — that approximate 

 equality would not be attained for many hundreds, 

 or in some cases thousands, of years. One of these 

 factors, convection, may be due to lightness, pro- 

 duced either bv high temperatures or by low atomic 

 weight, and a study of these two characteristics 

 will show at once that the two are tending to 

 counteract one another. 



^^'e have already referred to the fact that atom 

 sorting, or molecular escape, will tend to leave 

 behind, in the third body, a rotating swarm of 

 nebulous meteoric dust. In most cases, a good deal 

 of this may be associated with the torn suns, and 

 the torn suns would also, by the extraordinary 

 violence of the volcanic ejection, tend to produce 

 vast atmospheres. It is clear these atmospheres 

 must tend greatly to alter the character of the 



a Persei. photographed at the Verkes 

 hey. September 20th. 1910. 



