April 17, 18S5.] 



♦ KNOWLEDGE 



317 



AN ILLUSTRATED 



MAGAZINE OF SCIENCE 



^BilNIYWORDED-EyJlCTLYDESCmBED, 



LONDOX : FBI DA F, APRIL 17, 1885 



Contents of No. 181. 



M»t«on ud Falling Stars. Bj 

 Richard A. Proctor 317 



Pleasant Hoanwith the Microscope. 

 Bt H. J. Slack 318 



Optical Becreations. (lUtu.) Bj- 

 r R A S 319 



The PhiiosophT of Clothing. VI. 

 By W. Mattien Williams 321 



Is the Diameter of the Pupil of 

 the Eve an Equivalent of the 

 Light's Intensity ? (concluded). ., i^ 



Other Worlds than Ours 323 



Chapters on MMem Domestic Eco- 

 nomy. Xilll. (/Hi«.) 323 



Simple Methods of Making Lantern- 

 Slides. By W. J. Harrison 328 



TASB 



Production of Iodia-ru*iberin Brazil 327 

 Critical Methods of Detecting Errors 

 in Plane Surfaces. (lUus.) By 



John A. Bra»hear 337 



The Working Power of Man. By 



M. C. Meigs 329 



Editorial Gossip 330 



Reviews 331 



Electric Light and the Projection of 



Shadows 331 



Correspondence 332 



Our Mathematical Column : Mathe- 

 matics of Meteoric Astronomy. 



By Richard A. Proctor 335 



Our Inventor" Column 336 



I Our Chess Column 337 



METEORS AND FALLING STARS. 



By Richard A. Proctor. 



A DISCOVERY has been recently made respecting 

 meteors, by Mr. Denning, of Bristol, which throws 

 quite a new light on the subject of meteoric astronomy. 

 The interpretation of the discovery is indeed marvellous, 

 — and but one interpretation is possible. Thus, when four 

 or five years ago Mr. Denning announced the discovery as 

 already to all intents and purposes made, I felt that the 

 probabilities against what the discovery seemed to prove 

 were so great that even the apparently overwhelming 

 evidence collected by Mr. Denning did not suffice to esta- 

 blish the discovery as real. It seemed to me then, and 

 even now something of the same feeling remains — against 

 my own judgment^that the startling nature of the deduc- 

 tion from the evidence, was such as to make the evidence 

 itself seem untrustworthy. Yet was there much to tempt 

 me at any rate to accept Mr. Denning's evidence and the 

 conclnsion deducible from it. Despite our consciousness 

 that science requires us to consider the truth only, not 

 what we have thought and therefore wish to be true, we 

 cannot, even in the most earnest search after new truth, 

 but feel some interest in finding conclusions right which 

 we have carefully reasoned out. Now if Mr. Denning's 

 discovery were real, I saw that a theory respecting the 

 origin of meteors which I had advanced several years 

 before, would be supported by such strong evidence that it 

 would be rendered much more obviously probable than it 

 had thus far appeared to be. Possibly this had something 

 to do with my unwillingness to accept Mr. Denning's dis- 

 covery as real. I have learned to look with suspicion on 

 all evidence which I vish to find true. Just as I examined 

 with perhaps unnecessary caution Mr. Brett's fancied 

 recognition of the solar corona when the sun was not 

 eclipsed, because I was then specially interested in showing 

 that the corona is not a mere phenomenon of eclipses, 

 so I looked with doubt on Mr. Denning's startling dis- 

 covery of meteor systems with permanent radiants because 

 if that discovery were real the theory I had maintained 

 respecting the origin of meteors would be the only theory 



bv which the discovery could possibly (so far as I can 

 see) be explained. 



1 propose now to discuss afresh what had been already 

 learned respecting meteors and falling stars before Mr. 

 Deunin" made the discovery whicli he announced several 

 years a^o, and nisiy now bo said to have established. This 

 is a necessary preliminary to the exiilanalion of the true 

 meaning of his discovery. 1 niay remark in passing that 

 on this last point as I explained years ago, and particularly 

 noticed in communications addres.sed to Mr. Denning 

 himself, there can be no manner of doubt or question. 

 Admitting his discovery, as I now do (because he has 

 established it by sutlicieut observations), the interj)retation 

 though utterly amazing is unmistakable. Mr. Denning 

 seems to tbink this is not to, that accepted theories have 

 to be abandoned, and that, even when that has been done, 

 his discovery remains unexplained and probably inexpli- 

 cable. But "as a matter of fact the difficulty with his 

 discovery is that it is so obviously explicable in only one. 

 way. Other theories have not to be given up. What has 

 been already proved respecting the orbits of meteors 

 remains still established : it is set on too firm a basis to be 

 shaken by any discovery whatsoever. But the meteors 

 to which Mr. Denning's discovery relates, form a class 

 respecting which entirely new ideas mu.st be adopted. 

 Their existence is no more inconsistent with the doctrine 

 before held (and really demonstrated) respecting the 

 November meteors, the August meteors, and other such 

 systems, than the existence of comets is inconsistent with 

 the doctrine that planets travel in nearly circular paths 

 around the sun. But precisely as the theory of circular 

 orbits will not serve us in dealing with comet", so the 

 theories which have been demonstrated respecting meteor 

 systems travelling in closed orbits utterly fail us in dealing 

 with the meteors which seem to pour in upon the solar 

 system for months (aye and for years) in succession, from 

 the same regions of the star depths. 



Let me remark at the outset that some of the mathe- 

 matical relations involved in the discussion of my subject, 

 though by no means difficult, are not suited to such an 

 article as the present is intended to be. Here, therefore, 

 I shall content myself by using, as wanted, the results 

 which mathematical inquiry indicates. Elsewhere in these 

 pages I will present so much of the mathematical inquiry 

 as may be necessary for the elucidation of my subject. 



We start then with the theory established, as I have 

 already mentioned here, by Olmstead of America, — that 

 shooting-stars and meteors are bodies which enter our 

 earth's atmosphere from outside, and had been travelling on 

 parallel paths as they thus entered the air, those parallel 

 paths being parts of their orbits around the sun. Olm- 

 stead could prove nothing about the real nature of the 

 paths along which meteors travel, except that the sun must 

 be the ruling body whose attractions the meteors obey, and 

 that although the meteors travel in flights, each individual 

 meteor may be regarded as a tiny planet until its career 

 is brought' to a close in our own air. It has always 

 seemed to me to afford fine proof of the quality of Hum- 

 boldt's mind, that though not himself an astronomer, he 

 recognised the fulness of the evidence in favour of this 

 astronomical interpretation of meteors and falling stars, at 

 a time when mathematical and jirofessional astronomers for 

 the most part pooh-poohed Olmstead's theory as scarcely 

 worth thinking about. 



There could be no doubt, even in Olmstead's time, that 

 the theory which he had advanced respecting meteors was 

 sound. First the occurrence of displays of meteors on par- 

 ticular days in the year proved that these bodies must 

 travel around the sun in systems, each system crossing our 



