November 1, 1888.] 



♦ KNO^WLEDGB ♦ 



15 



has thrown the stars farther into space in corresponding 

 proportion, so that, instead of the stars' distances being 

 measured by thousands of millions of miles, they must be 

 measured by millions of millions, perhaps by hundreds or 

 thousands of millions of millions of miles. Yet now the 

 doubts of Tycho Brahe have entirely vanished. We know 

 that what he rejected as impossible is the simple truth. 

 Nay, the discoveries made with the telescope show that what 

 he held so marvellous is but the merest nothing compared 

 with the real truth. For, far beyond the stars of which 

 Tycho Brahe knew, exceeding them millions of times in 

 number, lie the stars revealed by the telescope, and these also, 

 like their brighter and (on the whole) nearer compeers, show 

 no measurable displacement as the earth circles round her 

 mighty orbit, a hundred and eighty-five millions of miles in 

 span. 



A discovery recently made leads to a result almost as 

 amazing as that rejected by Tycho Brahe ; nay, so amazing 

 that it has long led astronomers to reject, as he did, 

 what would have seemed fairly demonstrated were it not 

 for the incredible nature of the conclusion which must be 

 accepted along with it. In this case, as four centuries 

 ago, it is the earth's orbital motion which is in question. I 

 might, indeed, almost say that the earth's orbital motion 

 would be rendered doubtful by the new discovery, if the 

 accumulated proofs of the earth's levolution around the sun 

 were not overwhelming. Again it has been shown that the 

 earth's motion around the sun, vast though her orbit is, and 

 tremendous the velocity with which she moves, produces 

 no appreciable effect where one would expect its efl'ect to be 

 most marked. 



Meteoric astronomy has latterly been fruitful in remark- 

 able discoveries. Within the last quarter of a century, the 

 position of meteors in the universe has been made more and 

 more remai'kable by a series of discoveries of singular 

 interest. The views of Prof. Olmstead, of Hartford, Connec- 

 ticut, which had been overlooked save by a few of the bolder 

 thinkers w4ien first advanced, have not only been established, 

 but details which he could not indicate have been deter- 

 mined, and meteor systems shown to be far more remarkable 

 even than he had imagined. They have been I'ecognised as 

 crossing our own earth's track in hundreds, while within the 

 solar system astronomy has learned to recognise millions of 

 millions, not of meteors, but of meteor systems, each con- 

 taining trillions of trillions of individual meteors within its 

 limits. And now peculiarities have been recognised which 

 compel us to raise our conceptions of the range and number 

 of these systems far liighor, to recognise them as including 

 not only interplanetary systems countless in number, and as 

 we had thought amazing in range and extent, but as ex- 

 tending into the intei'stellar depths, across those seemingly 

 illimitable spaces which separate our sun from his fellow-suns 

 among tho stars. Moreover, we recognise that even our 

 ideas respecting the origin of these bodies must be widened, 

 that theories which had been regarded as reasonable and 

 probable must be rejected, and other theories which had 

 seemed too amazing to bo thought of, must be entertained. 



iiCt me here briefly recapitulate the evidence on which 

 acce[)t.ed theories (hero I speak of theories really accepted 

 and demonstnited) had been based, in order that the bearing 

 of the new discovery may bo clearly recognised. 



It had been shown by Olmstead that because showers of 

 falling stars, of tho same character, recur on particular days 

 (or nights) of tho year, therefore they must be due to tho 

 earth's passage through flights or streams of meteors crossing 

 her orbit at certain definite points ; for a day in the year is 

 tlie time when the earth in her motion around tho sun 

 reaches a particular part of her orbit. He had shown 

 further that the behaviour of meteors belonging to these 



showers corresponds with this theory, or rather with this 

 demonstrated fact ; for they are invariably found to radiate 

 from a particular point, or small region, of the heavens. 

 That is to say, if the tracks of the meteors seen during any 

 great display are marked down on a celestial globe, or on a 

 map so planned that the paths of meteors, however long, 

 would be represented by straight lines, these tracks, carried 

 backwards in great circles on the globe, or in straight lines 

 on the map, all pass through or very near a certain fixed 

 point on the celestial sphere. It matters not where the 

 observer may be who watches the display — in England, or 

 in America, or in Asia, Africa, or Australia — the same law 

 holds : except for straggling meteors which belong to other 

 systems, every meteor of the display has a track which, 

 carried backwards, is found to extend from the proper 

 " radiant point " for that system, the radiant being unchang- 

 ing among the stars. Nor does it matter how long the 

 display may last, or how far the radiant may be shifted with 

 respect to the horizon ; among the stars it always has the 

 same position. Olmstead showed the meaning of this, though 

 indeed the meaning should be obvious. A series of parallel 

 lines, or lines directed to the same point in remote space, 

 always appear to radiate from a point, if they are complete ; 

 and if parts of them only are seen (as is of course the case 

 with meteor tracks), these parts always have directions 

 radiating from that point. Hence meteor paths in our 

 atmosphere are all parallel : and as the point from which 

 they radiate is unchanging in the star-sphere, the direction 

 of parallelism does not change as the earth i-otates, and the 

 paths must therefore have been parallel before the meteors 

 entered the air. Thus, the meteors are bodies travelling 

 with velocities so great that neither the motion of the 

 observer round the earth's axis, nor the eflfect of tlie eai-th's 

 attraction on the meteors as they near her, has any eflfect in 

 altering either the apparent or the real direction of meteoric 

 motion. 



This demonstrated result was far from being generallj' 

 accepted. Alexander Humboldt, with that clear-sightedness 

 which characterised him, even when he was dealing with 

 matters outside his especial range of research, accepted 

 Olmstead's conclusion at once. He recognised meteors and 

 falling stars as travelling with planetary velocities, and even 

 described them quaintly as " pocket planets." 



lu 18GG new light began to be thrown on Olmstead's 

 demonstrated theorj-. It was found, first, that the orbits of 

 some meteor systems are such as to carry the meteor families 

 far beyond the paths of even the remote planets Uranus and 

 Neptune. Then it was discovered that .some meteor flights 

 travel in the tracks of known comets, as the August meteors 

 in the path of the bright comet of 1862, the November 

 meteors in the path of Tempel's comet of 1866 — one having 

 a period of 105 years, the other a period of 'i'i^ years. But 

 this was not all. Recognising the connection between 

 comets and meteors as demonsti-ated, I threw out in 1872 

 the suggestion, or prediction, that when the earth cro.ssed, 

 during the last week of November, the path of Biela's comet, 

 which in that year had crossed the earth's jiath (though, 

 broken up and "disintegrated as the comet had long since 

 been by tho sun's action, no telescope had detected its filmy 

 texture), there would probably be a display of falling stirs; 

 and on the night of November 27, 1872, the display was 

 seen. Hundreds of thousands of falling stars, all nidiating 

 from the part of the heavens corresponding to the known 

 track of the comet, were seen that night ; and the whole of 

 the radiant region, at one part of the display, was full of 

 amber-tinted light. Here, then, was another meteor system 

 associated with a comet, and that, too, in a manner whicli 

 removed even such shreds of doubt as might still have 

 remained in the minds of the more cautious astronomers. 



