May -22, 1SS5.] 



♦ KNOWLEDGE ♦ 



427 



\N ILLUSTRATED^ ^>t^ 



MAGAZINE OF SCIENCE ^^ 

 PuiNLYWoRDED-EXACTLY Described 



LOXDOX: FRIDAY, J/,1 )' 22, 1S85. 



OONTKN'TS OP No. It^O. 



PACK 



:tfeteors and Falling Stars. By R. A. 

 Prooior 427 



Oar Household Insects. {Illut.) By 

 B. A. Butler 42S 



Overhead Electric Wires. By W. 

 Slinjo -129 



Thought aud Lanf^na^e. IX. By 

 • AdaS. Ballin 430 



Chat?* on Geometrical Measurement. 

 {lUut.) By R. A. Proctor 431 



Xobert's Ruling Machine. By John 

 Mayall, jon 433 



Chapters on Modem Domestic Eco- 

 nomy. XXVUI. (Jllus.) 433 



PAQB 



Xervons Exhaustion. I. By Edwin 



Wooton 135 



Railwav Plant at the Invijjuions 



Exhibition 436 



Evnlution of the Sense of Beauty. 



By Conatan.e C. W. Xaden 437 



Origin and Home of tht* Diamond 



{Illm). By W. J. Harrison -139 



Editorial Gossip 440 



Reviews 4-11 



Face of the Sky. By F.K.A.S 1-13 



Correspondence 44a 



Our Inventors* Column 447 



Oar Chess Column 448 



METEORS AXD FALLING STAES. 



By Richard A. Proctor. 



( Continued from p. 405.) 



THE application of these considerations to Schiaparelli's 

 theory is easily perceived. In order that a jiarticle 

 attracted from outer space may be compelled to ti'avel in a 

 closed orbit around the sun, its velocity must be diminished. 

 And this can very readily happen. But for the particle to 

 travel in an orbit of a particular extent or mean distance, 

 its velocity where it crosses the distance of the disturbing 

 planet must be diminished by a certain amount ; and in 

 dealing with Schiaparelli's theory, it is a cardinal considera- 

 tion whether the observed orbits of periodic comets are such 

 that we can admit the po.ssibility of their resulting from any 

 diminution of velocity which the disturbing planet could 

 have produced. Take, for instance, the November meteors, 

 which pass near the orbits of Uranus and the earth, and do 

 not approach any other orbit near enough for any such 

 effects upon the orbital motions of these bodies as we are 

 now dealing with.* We may di.smiss the earth from con- 

 sideration at once, because our planet is far too small to 

 modify the motions of bodies rushing past her with the 

 velocity, nearly 2G miles per second, which the sun has com- 

 municated to bodies approaching him from interstellar space, 

 by the time they reach the earth's surface from him. 

 Uranus then alone remains. Now the present velocity of 

 the November meteors when crossing the orbit of Uranus, 

 amounts to about 1 ', mile per second. The velocity of a 

 particle approaching the sun from interstellar space would 

 be nearly six miles per second when at the distance of 

 Uranua It may be seriously questioned whether, under 

 any circumstances whatever, a particle crossing the track 

 of Uranus without encountering the planet could be 

 deprived of 4i miles per second of its velocity. For 

 though Uranus can deprive a body directly receding from 

 him (and starting from his surface) of a velocity of about 



* Both Jnpiter and Satnm can perturb the November meteors, 

 and thns modify the shape and position of the meteoric orbits ; bnt 

 such changes, rhongh by no means inappreciable, are utterly iusig- 

 m£cant compared with those required to change the motion of a 

 body approaching the sun from interstellar space into motion in an 

 orbit like that of the Kovember meteors. 



13 miles per second, yet the considerations above adduced 

 show that only a traction of tliis velocity could be 

 abstracted from a body iimving past Uranus ; and it is 

 certain that if so large a nnluction as 1.', miles per second 

 could bo cd'octeil at all, it would only be by a singularly 

 close approach of the particle to the .surlaco of Uranus. 



But setting apart the improbability that a body arriving 

 from interstellar space could bo in this way conii)(dltd to 

 travel in the orbit of the November uu^tcors, the possibility 

 of such a capture would not jirove the possibility of the 

 capture of a ilight of bodies largo enough to form that 

 meteor system and its accompanying comet. If the whole 

 material of the system and its comiit had arrived in a com 

 pact body, the material attractions of the ]iarts of that body 

 would be sufficient to keep them together ; whereas, in 

 point of fact, the November meteor-system and its comet 

 occupy at present a large range of space, even if tlu^ 

 meteors bo not .scattered all round the orbit (however 

 thinly along portions thereof). If, on the other hand, the 

 material of the V)ody were not in a compact form, the body 

 would be necessarily large, and a portion of it only would 

 be captured by Uranus. Nay, it is not even necessary 

 that this should be conceded. For though we admitted 

 that the whole of a large and tenuous body not kept 

 together by the mutual attraction of its parts or by cohe- 

 sion, might be captured, it is manifest that different parts 

 would be captured in different ways, and would thence- 

 forth travel on widely different orbits. That a system of 

 bodies already drawn out into an extended column, and in 

 respect of length already resembling the meteor systems we 

 are acquainted with, could be captured, as Schiaparelli's 

 theory requires, and all sent along one and the same closed 

 orbit, is altogether impossible. 



It is to be noticed also that we gain nothing, as respects 

 the interpretation of meteor systems or comets, by adopting 

 Schiaparelli's hypothesis. To assume that meteoric matter 

 has been wandering about through interstellar space, until 

 the sun's attractive influence drew such matter towards 

 the solar system, is to explain a difficulty away by 

 advancing another still greater ; moreover, we have not a 

 particle of evidence in support of the supposition. To 

 suppose, on the other hand, that meteor - flights 

 have crossed the interstellar spaces, coming to us 

 from the domain of another sun, is to remove the diffi- 

 culty only one steji. We know that comets pass away 

 from the domain of our sun to visit some other sun after 

 an interstellar journey of tremendous duration ; and to 

 suppose that comets, whether of hyperbolic or elliptic 

 orbit, came to us originally from the domain of another 

 sun, is merely to suppose that that happened to such 

 comets millions of years ago which we know to be haj>pen- 

 ing to other comets at this present day, but not by any 

 means to expdain the nature of comets or their origin. We 

 know that many comets leaving our system to visit others 

 had not their origin within our system ; and we cannot 

 a.ssume as possible or even jjrobable that any comet had its 

 origin within the domain of another sun than ours, unless 

 we assume as possible or probable that some among the 

 comets leaving our own sun had their origin within our 

 sun's domain. And what is here said of comets must be 

 understood as applying to meteor systems. 



Thus, then, we are led to the conclusion that whether we 

 adopt, with Schiajiarelli and others, the theory that comets 

 or meteoric .systems can be drawn into the solar domain, 

 or regard such an event as of very infrequent occurrence, 

 or reject it as impossible (which we safely may), we still find 

 that the origin of comets must be looked for within solar 

 systems ; or rather, since we cannot claim to trace back 

 comets any more than planets or tuns, to their actual 



