190 



♦ KNO^A^LEDGE ♦ 



[July 1, 1889. 



would take to travel from the nearest star to our own 

 system ; while in my essay in the Xorth American Review 

 on the Origin of Comets and Meteors 1 had spoken of many 

 meteoric bodies as certaialy reaching our earth from the 

 interstellar depths, and primarily- from the interiors of the 

 fixed stars. But the idea had not presented itself to my 

 mind that streams of meteor.? from remote suns could retain 

 after their journeys across the interstellar depths velocities 

 of many hundred miles per second, or that such streams 

 could at our distance from even the nearest stars retain so 

 much of the character of streams that the passage of the 

 earth through any such system should indicate the position 

 of their radiant point. Still less did it seem likely to me 

 that such streams should remain recognisiible by meteors 

 observable not only for several successive months in one 

 year, but during several successive years. 



Thus, like Professor Alex. Herschel, Mr. Greg, and others, 

 I regarded Mr. Denning's observations as insufficient to 

 establish so marvellous a result as they would unquestion- 

 ably demonstrate if accepted. I did not reject them ; but 

 it appeared to me that they should not be accepted until 

 overwhelming evidence bad been obtained in their favour. 

 Thus I waited, though fully recognising the validity of what 

 Humboldt said in his "Physical Description of the Heavens," 

 speaking, more than a (juarter of a century ago, on this very 

 subject : — "The progress of our knowledge, respecting igneous 

 meteors," he said, " will be the more rapid the more im- 

 partially facts are separated from opinions, so that while 

 carefully sifting or testing all particular facts on the one 

 hand, we may not, on the other, fall into the error of reject- 

 ing, as bad or uncertain oljservations, whatever results we are 

 not yet able to explain." "It appears to me most import- 

 ant," he went on, " to separate physical relations from those 

 geometrical and numerical relations which admit, generally 

 speaking, of more certain and assured investigation." Only, 

 it is to be noticed that the trouble with Mr. Denning's 

 observations was not at that time that they were not easy to 

 explain. Mr. Denning himself appears still to imagine that 

 this is the difficulty. The real source of perplexityl.ny, and 

 the real interest of his discoveries lies, in this, that they can 

 bear but one explanation, and that that exjilanation is so 

 singular and so interesting. 



There is, as I pointed out to Mr. Denning four years ago, 

 but one explanation of a meteor-stream having an unvary- 

 ing radiant for several months in succession — viz. this, 

 that the component meteors are travelling on parallel 

 paths through the interstellar depths, and cross our solar 

 system with such velocities, that during their passage 

 athwart the domain of the sun their paths are hardly 

 deflected at all, at least until they are far within our earth's 

 distance from the sun. Thus the e.arth's atmosphere receives 

 them on nearly parallel paths ; though perhaps such as fall 

 on Venus and on Mercury may have had their directions 

 appreciably altered, because of the more energetic solar 

 attraction to which they have been exposed. For the same 

 reason that the influence of the sun at the earth's distance 

 does not .affect the real course of these swiftly-travelling 

 meteors, the varying direction of the earth's motion does not 

 influence their apparent direction: a velocity of 18| miles 

 per second is as nothing compared with the " swift rush of 

 those meteors through space. 



It was because of the unlikely nature of this — the only 

 possible explanation of Mr. Denning's discovery— that until 

 the discovery should be confiirmed by sufficient evidence I 

 regarded it as doubtful. As a problem of probabilities, the 

 unlikelihood of the conclusion cerbiinly deducible if the 

 observations were trustworthy, overbalanced then the evi- 

 dence—strong though it seemed — in favour of the facts 

 supposed to have been observed. 



Observations have now, however, continued long enough 

 to make further doubt respecting their general validity un- 

 reasonable, and the balance of probabilities is so far turned 

 the other way that we may begin to inquire in ir/iaf degree 

 the observations may be accepted. Carefully weighing the 

 evidence gathered by Mr. Denning himself, and combining 

 it with that which Messrs C!reg, A. Herschel, Konkoly, 

 and others have obtained, the prob.ability of error, or 

 that merely accidental coincidence is in question, becomes 

 so small, that even the seemingly immense unlikelihood of 

 the conclusion to which the observations \inmistakably 

 point, disappears. We have to accept the observations, and 

 with them the inferences deducible from them. We learn that : 

 Besides the meteors ivhich form systems travellin;/ on closed 

 paths around the sun, besides those meteors which had been 

 recognised as coming from interstellar space with velocities 

 not greatly exceeding those irhich our sun can communicate to 

 bodies ap2)roaching him from a distance, and besides those less 

 certainly recognised luhich have been regarded as ejected 

 from the earth herself in past ages, there are some vhich 

 reach our solar system icitli irhat may be described as extra- 

 planetary velocities — icith velocities so great that the earth's 

 velocity in her orbit is by comparison small. 



Only, it must be remarked that Mr. Denning's observa- 

 tions cannot be accepted as interpreted by him. ([ am not 

 referring to any explanation he offers, for he offers none — 

 seeming, indeed, to be of those who loss interest in observa- 

 tions, even their own — when apparently pointing to any- 

 thing so unworthy of esteem as new truths.) He speaks of 

 his "radiants " as staii'ojirtry, which is impossiVile. When 

 pushed, he claims to determine them within a couple of 

 degrees. It is not only altogether unlikely that they change 

 so little as this, it is absolutely impossible that ^Slr. Denning, 

 or even Mr. Greg or Professor Herschel, could determine 

 the radiant point of meteors, even during a one-night 

 shower, within five or six degrees. If we admit that some 

 radiants seem to change so little, in several months, as to 

 indicate velocities up to one hundred miles a second, that 

 will correspond with !Mr. Denning's observations — as 

 reasonably interpreted — and be quite remarkable enough 

 even then. 



Schiaparelli's vague guess respecting the origin of meteors 

 (oddly described by Professor Young a.s " the received 

 theory") fails utterly in the presence of this apparently 

 recognised fact : my own susgestion on the .same problem, 

 based as it was on strong evidence, both positive and nega- 

 tive, not only does not fail, but actually makes the very 

 result which seems so amazing antecedently probable. Let 

 us consider : — 



In my theory appeared three classes of bodies as parents 

 of meteor- systems : — First, the e.arth and her fellow terres- 

 trial planets, as the parents — when in the sunlike stage — of 

 minor families of meteors crossing severally the tracks of 

 their generating orbs; secondly, the giant planets, as the 

 parents when in the sunlike stage, possibly even now, of 

 meteor-.sy.stems travelling around the sun, but crossing the 

 orbits of the giant planets from which they respectively 

 came ; thirdly, our sun and his fellow suns, as the parents 

 of families of meteors which only pay occa.sional visits to 

 other sol.ar systems th.an those from whose ruling centre they 

 originally proceeded. Is there no higher order of bodies 

 which might have generated meteors travelling with the 

 gi-eater velocities now recognised? Undoubtedly there is 

 a class of bodies which not only might have genei-ated such 

 velocities, but, if my theoiy of the origin of meteors is sound, 

 might be expected to have ejected meteors with velocities 

 of those high orders. There are the giant suns, like Sirius 

 and his fellows, so enormou.sly surpassing our own sun, and 

 those among the stars which must be regarded as his fellows, 



