122 



KNOWLEDGE. 



[June, 1903. 



system of wliich our sun is a preponderating star. Tb 

 Milky Way is made u]j of an agglomeration of clusters of 

 stars dis]>osed pretty nearly in the same fairly wide plane. 

 The telescope has disclosed a great number of clusters 

 of stars and of nebulte — about six tht)Usaud. But if we 

 place on a chart, representing the two celestial hemispheres, 

 these clusters and uebuliB, a fact is made clear worthy of 

 the greatest attention. It is that most of the clusters are 

 gathered into the plane of the Milky Way, and that most 

 of the gaseous nebulas are collected, on the contrary, away 

 from this plane, and near the poles of the Milky Way. 



This has a significance of great importance to our 

 knowledge of the structure of the sidereal universe. 



On the other hand, if we examine the law of distribu- 

 tion of stars in the sky, we ascertain that their numbers 

 gradually increase — for all magnitudes — in proportion as 

 we approach the Galaxy. 



But it is of consequence to note that neither for stars 

 nor for stellar clusters is this condensation uniform. It is 

 not, for example, by zones parallel to the Milkj' Way that 

 we must proceed, for that method is insufficient, but by 

 the direct examination of the sky. If we trace isophotic 

 charts giving the sidereal density as is done on hypso- 

 metrical charts for contour relief, these differences are 

 made evident. 



On a clear summei- niglit, our eyes, trained astro- 

 nomically, can observe in this vast celestial girdle of the 

 Galaxy very different stellar densities, and we gain the 

 impression that far from being a regular system, coui- 

 jiai'able to the solar system, for instance, the Milky 

 Way is a perspective image formed by the superposition 

 of an innumerable multitude of stellar clouds, scattered 

 over immense distances in one chief plane. We see it 

 divided into two unequal branches in Cygnus and the 

 Scorpion, and rent here and there into numberless stars. 

 Our sun is no moi-e at the centre than his neighbour 

 Alpha Centauri (which lies about forty-one trillions of 

 kilometres from us) or than our other neighbour 61 Cygni 

 (about sixty-nine trillions distant) — both right in the 

 plane of the Milky Way — or than the majority of the stars 

 whose parallaxes have been measured. These stars are 

 distant fi'om us several light-years, whilst the limits of 

 the Galaxy are situated at thousands of light-years. 



Not only does our sun not mark the centre of our 

 universe more than our neighbours in space do, but it 

 has no greater weight than they. Alpha Centauri is a 

 splendid binary system and its mass is more than twice 

 the sun's. We do not know what planets may cii-culate 

 round one or other of these two stars, whose mutual 

 revolution is nearly a century. It is not surprising that 

 we cannot see them, since if our sun were at their distance 

 Jupiter would be a star of the 24th magnitude, separated 

 by 4" from the sun, which would itself be of but the 

 second rank. Seen from the distance of stars of the 1st 

 magnitude, themselves very diverse, our sun would appear 

 but of the third, fourth, fifth or sixth rank, and might be 

 even invisible from Kigel or Canopus, which have no 

 measurable parallax. The mass of Sirius is equal to that 

 of four suns. Vega is seventy times as bright, and 

 Canopus sui-passes the sun in brightness by more than ten 

 thousand times. Dr. Wallace's theory might be excusable 

 for an inhabitant of the systems of Sirius or Capella or 

 Antares, but not for a dweller in our own modest hamlet. 

 If there were a central sun, and if that central sun were 

 ours, the illusion might be granted. But there is nothing 

 of the kind. The solar system is a monarchy with the 

 sun for autocrat Our sidereal universe is a republic, a 

 federation without a dominating authority. 



According to the calculation of Lord Kelvin, the amount 

 of the proper motions of the stars indicates that the 



number of the suns of our sidereal universe does not seem 

 to exceed one thousand millions. The force of gravitation 

 of these suns, taken in the mean to be similar to our own, 

 woiild produce the velocities observed of twenty to one 

 hundred kilometres per second. A number ten times 

 greater could only have been deduced if those movements 

 were much more rapid. Granted this milliard of stars, it 

 in no wise proves that it alone exists in the infinite, and 

 that beyond an immense void there may not be a second 

 milliard, nor a third, nor a fourth, nor more. Whatever 

 may be its extension, our Milky Way is but a point in the 

 infinite. 



It would even now a])]jear that we know of stars which 

 do not belong to our sidereal system. We might cite with 

 Newcomb, the star 1880, Groombridge, the swiftest of those 

 whose motion has been detennined, its speed exceeding 

 300,000 metres per second. The attractive force of the 

 milliard of stars of which we have just spoken would not 

 api:)ear sufficient (except under special circumstances) to 

 produce such a velocity, and many astronomers think that 

 this star has come from the beyond, and traverses our 

 universe like a projectile. This star is not the only one 

 in such a case. 



On the other hand, certain globular clusters do not seem 

 to form a part of our agglomeration. 



This agglomeration represents a universe. It approxi- 

 mates, in spite of its heterogeneity, to the general form of 

 a flattened spheroid, of which the Milky Way marks the 

 equator. Facts seem to indicate that the forces which 

 influenced its evolution exercised their greatest intensity 

 and activity in its equatorial zone rather than at the 

 circvimpolar regions, which have remained backward, less 

 dense in actual stars or in those in the making, colder, 

 and, so to speak, benumbed. Everything is more advanced 

 in the equatorial region than at the poles. Our sun itself 

 appears to be in its summer. There red stars are crowded, 

 and there also are temporary resurrections. 



On the whole, then, the astronomical theory of the dis- 

 tinguished naturalist has not been established, and, in fact, 

 is quite inadmissible. It would be superfluous, therefore, 

 to occupy ourselves with its biological consequences rela- 

 tive to oui' planet, the assumed object of the creation. In 

 our solar system, this little earth has not obtained any 

 special privileges from Nature, and it is strange to wish to 

 confine life within the circle of terrestrial chemistry. Nor 

 is it less so to see a naturalist (whose theories of evolution 

 demand the action of time as the principal factor in the 

 succession of species) forgetting that the epoch in which 

 we now happen to be has no special importance ; that the 

 different worlds of our solar family are at diflierent stages 

 of their evolution ; and that, for instance, if the Moon is a 

 waif of the past, Jupiter, on the contrary, is a world of the 

 future. The effect of the hypothesis of Dr. Wallace is to 

 narrow our horizon, and to take us back again to the time 

 of Ptolemy, into the prison of a useless firmament. The 

 greatness of modern astronomy, on the contrary, is to 

 burst all barriers, for our science is but a shadow in the 

 face of the reality. Infinity encompasses us on all sides, 

 life asserts itself, universal and eternal, our existence is 

 but a fleeting moment, the vibration of an atom in a ray 

 of the sun, and our planet is but an island floating in the 

 celestial archipelago, to which no thought will ever place 

 any bounds. Never lose sight of the fact that space is 

 infinite, that there is in the void neither height, nor depth, 

 nor right nor left ; and in time neither beginning nor end. 

 We must understand that our conceptions are relative to 

 our imperfect and transitory impressions, and that the 

 only reality is the Absolute. 



What right have we then to suppose that the limits of 

 our knowledge are the limits of the power of Nature? 



