TRANSLATION OF THE SUN IN SPACE. 



45 



sphere now indicated, there is great probability 

 in the hypothesis which assumes the existence 

 of an extremely oblate ring of nebulous or va- 

 porous matter revolving freely in space be- 

 tween the orbits of Venus and Mars, as the ma- 

 terial cause of the zodiacal light("). Mean- 

 time, of its proper material dimensions, of its 

 increment by emanations from the tails of myr- 

 iads of comets which approach near to the 

 sun("), of the singular variability of its extent 

 — for it seems at times not to extend beyond the 

 orbit of the earth, and lastly, of its very prob- 

 able close connection with the denser world- 

 ether in the vicinity of the sun— nothing cer- 

 tain can be concluded. The vaporiform par- 

 ticles of which the ring consists, and which 

 circulate about the sun in conformity with plan- 

 etary laws, may either be self-luminous, or 

 lighted by the sun. Even a terrestrial haze or 

 fog (and the fact is very remarkable) appeared 

 at the time of the new moon (1743), which at 

 midnight was so phosphorescent that objects 

 at the distance of 600 feet could be plainly dis- 

 tinguished by its lightC*^). In the tropical cli- 

 mate of South America, the variable strength 

 of light of the zodiacal gleam struck me at 

 times with amazement. As I there passed the 

 beautiful nights in the open air, on the banks 

 of rivers and in the grassy plains (Llanos) for 

 several months together, I had opportunities of 

 observing the phenomenon with care. When 

 the zodiacal light was at its very brightest, it 

 sometimes happened that but a few minutes 

 afterwards it became notably weakened, and 

 then it suddenly gleamed up again with its 

 former brilliancy. In particular instances, I 

 believed that I remarked — not any thing of a 

 ruddy tinge, or an inferior arched obscuration, 

 or an emission of sparks, such as Mairan de- 

 scribes, but a kind of unsteadiness and flicker- 

 ing of the light. Is it that there are ^ny pro- 

 cesses going on in the vaporous ring itself 1 or 

 is it not more likely that, though I could detect 

 no change, by the meteorological instruments, 

 in the temperature and moistness of the re- 

 gions of the atmosphere immediately above the 

 ground, and though small stars of the fifth and 

 sixth magnitudes appeared to shine with undi- 

 minished strength of light, that in the superior 

 strata of the atmosphere condensations were 

 proceeding which modified the transparency, or 

 rather the reflection of the light, in a peculiar 

 and, to us, unknown manner 1 For the as- 

 sumption of such meteorological processes on 

 the limits of our atmosphere, the "explosions 

 and pulsations" observed by the acute 01- 

 bers(^^), " which, in the course of a few sec- 

 onds, went trembling through the whole of a 

 comet's tail, with the effect now of lengthening, 

 now of abridging it by several degrees," appear 

 to vouch. " As the several parts of the mill- 

 ions-of-miles-long tail are at very different dis- 

 tances from the earth, the laws of the velocity 

 and propagation of light do not permit us to 

 suppose that actual alterations in a body filling 

 an extent of space so vast, could be perceived 

 by us in such short intervals of time." These 

 considerations by no means exclude the reality 

 of varying emanations around the condensed 

 nuclear envelopes of a comet, the reality of 

 suddenly supervening brightenings of the zodi- 

 acal light, through internal molecular move- 



ments, through alternately augmented or di- 

 minished reflections of light by the matter of 

 the luminous ring; they should only make us 

 careful to distinguish between them and all that 

 belongs to the celestial ether — to universal 

 space itself, or to the aerial strata composing 

 the atmosphere through which we see. What 

 in other respects takes place in the outer limits 

 of our atmosphere — the subject of great diver- 

 sity of opinion — is, as well-observed facts in- 

 dicate, by no means to be completely or satis- 

 factorily explained. The wonderful lightness 

 of many whole nights of the year 1831, in which 

 small print could be read at midnight in Italy 

 and the north of Germany, is in obvious con- 

 tradiction with all that the latest and ablest ob- 

 servations on the crepuscular theory, and the 

 height of our atmosphere, make known(^''). 

 Luminous phenomena are dependent on con- 

 ditions that are yet unexplored, the unstable- 

 ness of which, within the limits of the twilight, 

 as well as in connection with the zodiacal 

 light, strike us with astonishment. 



Thus far we have considered what belongs 

 to our sun, and the world of formations that is 

 ruled by him — the primary and secondary plan- 

 ets, comets of shorter and longer periods of 

 revolution, meteoric asteroids which move sin- 

 gly in closed rings, or in multitudes like a 

 stream ; finally, a luminous nebulous ring which 

 circles round the sun near to the orbit of the 

 earth, and which from its position may remain 

 with its name of zodiacal light. Every where 

 the Law of Return prevails in the motions, 

 how different soever the measure of the pro- 

 jectile velocity and the quantity of conglobated 

 material parts ; the asteroids alone, which fall 

 from space into our atmosphere, are interrupted 

 in their planetary round, and united to a larger 

 planet. In the solar system, whose limits the 

 attractive force of the central body determines, 

 comets, at the distance of forty-four times the 

 distance of Uranus from the sun, are compelled 

 to return in their elliptical orbits ; in these 

 comets themselves, indeed, whose nuclei, from 

 the smallness of the masses they comprise, 

 present themselves to us in the guise of flitting 

 cosmic clouds, these nuclei, nevertheless, bind, 

 by their attractive force, the very outermost 

 particles of the tail that is streaming away at 

 the distance of millions of miles from them. 

 The central forces, therefore, are the forming, 

 the fashioning, and even the preserving forces 

 of a system. 



Our sun, in its relations to all the returning 

 or circulating, greater or smaller, denser or al- 

 most vaporiform bodies that belong to it, may 

 be regarded as at rest ; yet does it revolve 

 around the common centre of gravity of the 

 whole system, which, however, still falls with- 

 in itself; which, in other words, despite the 

 variable position of the planets, still remains 

 attached to its material bounds. Altogether 

 different from this phenomenon, is the motion 

 of translation of the sun— the progressive mo- 

 tion of the centre of gravity of the entire solar 

 system in Universal space. This goes on with 

 such velocity, that, according to Bessel, the 

 relative motions of the sun and of the 61st star 

 in Cygnus do not amount to less than 834,000 

 geographical miles in a day("). This change 



