2f 



KNOWLEDGE 



[November 1, 1895. 



absorbed by the vaporization of the obscuring clouds, and, 

 this work ended, the temperature can never be higher than 

 before, since an increase of temperature would cause au 

 increase of dissociation of the molecules A B, while the 

 only source of heat is an increase of their association. 

 The restoration of the maximum being explained in this way, 

 the star's atmosphere is now filled again with the molecules 

 of the vaporized clouds, and the remaining molecules 

 A and B are, as before, prevented from combining. But 

 under the never-ceasing influence of the star's loss of heat 

 by radiation the saturated vapours will condense again in 

 obscuring clouds. The thicker these clouds become, the 

 nearer draws the moment of a new partial combination of 

 A and B, causing a new maximum by a new evaporation 

 of the minimum clouds, and so on. 



The more or less simultaneous evaporation of clouds in 

 an entire spherical layer of the star, which my theory 

 demands, would be impossible if the star's atmosphere 

 bore any resemblance to our terrestrial atmosphere, with 

 its irregularly distributed temperature. But since the 

 disturbances of our atmosphere, entirely due to an external 

 cause, viz., our sun (that is, to a cause which is not at 

 work on the stars), there is no reason why all the points 

 of any one spherical layer should not have the same tem- 

 perature, that temperature being only dependent on the 

 distance from the star's centre. The only cause which 

 would render it otherwise, would be some inequality in 

 cooling and some motion so produced. But, as the star's 

 atmospheres are necessarily rich in dissociated and 

 vaporized matter ready to condense and thus to produce 

 new heat, in proportion as the existing heat is lost by 

 radiation, a sudden fall of temperature is impossible in 

 it. Just as steam in losing heat cannot cool below 

 100^, as long as the whole mass has not been con- 

 verted into water, so no incandescent vapour can fall in 

 temperature as long as some of the molecules condensable 

 at this temperature remain unoondensed. Thus, if the 

 gaseous and vaporous mixture, which form the star's 

 atmosphere, has not yet reached this condition, it will 

 preserve its temperature and tranquillity, and we see then 

 no reason why all the points of the same spherical layer 

 should not have the same temperature. 



The current ideas of the enormous scale upon which 

 disturbances take place in the solar atmosphere are almost 

 wholly based upon the simplest interpretation of the 

 displacement of lines in prominences, but this interpretation 

 is not necessarily the only possible one. Secchi (Le Soleil 

 II., pp. 112, 124) and Young (The Sun, pp. 165, 161, 211) 

 have often stated that if the displacements did not exist, 

 they would ba prepared to consider the prominences as 

 formed where we see them, something like the deposition 

 of dew, or the propagation of a flame along a train of 

 gunpowder. M. Fenyi, when discussing my explanation 

 of the prominences as merely evanescent illuminations 

 caused by the propagation of chemical actions in com- 

 paratively tranquil matter (A. and A. 1891, p. 127), urges 

 the same objections, but adds, nevertheless : " We must 

 confess that not only do the enormous velocities observed 

 in these prominences find a welcome explanation in 

 Brester's theory, but that the details of the development 

 and the banded structure are brought into better accord.'' 

 If it be admitted that in prominences the displacements of 

 their lines do not prove their motions to be real, not 

 only the prominences themselves, but ako almost all other 

 solar phenomena, as, for example, the undisturbed strati- 

 fication of the solar atmosphere, become much more clear. 

 I tried to show this in my theory of the sun. 



Eecent publications give, I think, the impression that 

 there is a growing suspicion that spectral lines are liable 



to be displaced by other causes besides those of motion in 

 the line of sight. There is, for instance, the opinion of the 

 late President of the Eoyal Astronomical Society, Captain 

 W. de W. Abney, who, speaking at a recent meeting of 

 that society, about velocities of one hundred thousand miles 

 a minute in the solar atmosphere, concludes as follows : 

 " Whatever may be the cause of this, I think that we 

 need not come to the definite conclusion that it is absolutely 



I matter which is moving at this surprising velocity, but 

 that the appearance may proceed from other causes. We 



, have learned our lesson from test books where we are told 

 that such and such is the case regarding the prominences 



I and the sun's surface. It remains to be shown whether 

 the text books are right or whether new text books must 

 be written for the rising generation." (Obsen-atori/, 



I January, 1895.) (See also W. H. Monck, Publications 

 of the Astronomical Society of the Pacific, VII., p. 38.) 



My theory so far described, shows that a red variable 

 can be compared to a clock. Chemical combination of 

 dissociated matter, A and B, when cooling, being the 

 clock-spring when running down, and the intermittent 

 evaporation of dark condensed admixed matter E being 

 the escapement which slackens the running down and 

 regulates it. 



It is plain, however, that such a mechanism cannot work 

 with the regularity of a chronometer. Now, we know 

 that red variables never show exact regularity, and that on 

 the contrary their changes in brightness are often very 

 conspicuous. If for the most part they show a much more 

 rapid rise to maximum than fall to minimum (as, for 

 instance, i) Aquilae, E. Cass., T. Yulpec, E. Gemin., Mira 

 Ceti, Mira Cygni, X. Sagitt., etc.), if for the most part 

 their maxima have but a short duration, these common 

 features correspond most exactly with my explanation ; but 

 my theory foresees also a quite different behaviour. Slight 

 differences, for instance, in the chemical composition, and 

 misty condensation of difl'erent parts of the same cloudy 

 layer, will (also by producing some inequality in the emis- 

 sive and reflective powers of neighbouring places) cause the 

 cloudy layer not to be dispersed at once, but gradually in 

 process of time. In the latter case the maximum will be 

 neither so bright nor manifest, nor so punctual as in the 

 former. It will be a maximum with fluctuations. The 

 greatest irregularities can be expected, and even a complete 

 loss of periodicity, when the stock of molecules A and B 

 being finally exhausted, other molecules C and D, etc., 

 with difi'erent or too little affinity, fill their places. If such 

 great irregularities are not in discordance with my theory, 

 they seem hard to be reconciled to explanations which, like 

 the meteoritic theory of Mr. Lockyer, require a true orbital 

 revolution, usually a very accurate time-keeper. 



My explanation is also, I think, in agreement with the 

 spectroscopic observations. In the general obscuration of 

 the minimum spectrum we see the effect of the obscuring 

 clouds, and in the bright lines often observed, especially 

 in the maximum spectrum, the luminous effect of the 

 chemical combination producing a chemical luminescence, 

 there, as well as in our laboratories, where, for instance, at 

 a temperature of less than 150° sulphide of carbon pro- 

 duces a bluish flame with discontinuous spectrum* 



« E. Wiedemann : Pogg. Ann, (N. F.) 37, pp. 177— 2i8. E. v. 

 Hclmlioltz : Die Licht nnd Warme strahlung verbrennender Gase, 

 Berlin, 1890. E. Pringsheim : Wiod. Ann. 45, p. 428; 49, p. 347. 

 Paschen : Wied. Ann. 50, pp. 409 — 443. G-. Wiedemann : Die Lehre 

 von der Elektricitat und deni Magnetismns, IV., p. 526. W. 

 Siemens : Wied. Ann. IS, p. 311. Ebert : Vierteljahrsohrift d'Astr. 

 Gesellschaft, 1892, p. 3t. A. Smithells ; Phil. Mag., Jan. 95, 

 Astrophysical .Journal, I., p.' 266. E. Wiedemann u. G. C. Selimidt : 

 Wied. Ann., 1895, No 4, p. 604. Ebert : Astrophvs. Journal, .Tune, 

 1895, p. 55. 



