6 



KNOWLEDGE 



[Jantjaby, 1904. 



of the funtrus often assumes most fantastic forms, and is 

 generally brilliantly coloirred. Over this framework is 

 spread at maturity a dingy green, semi-fluid mass, intensely 

 sweet to the taste, and, from the ordinary human stand- 

 point, intensely fiptid ; the exceedingly minute spores are 

 imbedded in this substance, which is greedily devoured by 

 various kinds of insects, mostly flies, who thus uncon- 

 sciously diffuse the spores, as it has been shown that these 

 are not injured by passing through the alimentary tract of 

 an insect. It is interesting to note that in certain of the 

 fungi the same advertisements in the guise of colour, sweet 

 taste and smell, are used for the purpose of unconscious 

 dispersion of the spores by insects, as are used by 

 many flowering plants for the purpose of securing cross- 

 fertilization, also through the agency of insects. 



MODERN COSMOGONIES.* 



VI.— WOllLD-BUILDING OUT OF METEORITES. 



By Agnes M. Cleeke. 



The idea is seductive that we see in everv meteoric fire- 

 streak a remnant of the process by which our world, and 

 other worlds like or unlike it, were formed. It is not a 

 new idea. Chladni entertained it in 1794; and it has 

 since from time to time been revived and rehabilitated 

 with the aid of improved theoretical knowledge and a 

 larger array of facts. Survivals are tempting to thought. 

 It costs less effort to realise differences in degree than 

 differences of kind. The enhanced activity of familiar 

 operations is readily imagined ; while perplexity is apt to 

 shroud the results of modes of working strange to 

 experience. Hence the presumption in favour of con- 

 tinuity ; nor can it be said, even apart from our own 

 mental inadequacy, that the presumption is other than 

 legitimate. Nature is chary of her plans, lavish of her 

 materials. Her aims are characterized by a majestic unity, 

 but she takes little account (that we can see) of surplusage 

 or wreckage. Now it seems likely that meteorites represent 

 one or the other of these two forms of waste stuff. They 

 are analogous, apparently, either to the chips from shaped 

 blocks, or to the dust and rubbish of their destruction. 

 Let us consider what it is that we actually know about 

 them. 



It cannot be said that the sources of our information are 

 scanty. Fully one hundred millions are daily appropriated 

 by the earth as she peacefully pursues her way. Their 

 absorption leaves her unaffected. It produces no per- 

 ceptible change in her internal economy, and makes no 

 sensible addition to her mass. The hundred millions of 

 small bodies taken up have, nevertheless, in Professor 

 Langley's opinion, an aggregate weight of more than one 

 himdred tons.t And this increment is always going on. 

 Yet its accumidated effect is evanescent by' comparison 

 with the enormous mass of our globe. That it was more 

 considerable in past ages than it is at present, might Ije 

 plausibly conjectured, but cannot reasonably be maintained. 

 Geological deposits contain — unless by some rare excep- 

 tion — no recognizable meteoric ingredients. There is 

 nothing to show that the earth was subject to a heavier 

 bombardment from space during the Silurian era than in 

 the twentieth century. 

 . Meteorites signify their existence to us, in general, onlv 



* For former articles under this title see KyowiEDGE 1903 

 pp. 57, 104, 148, 196, 251. 



■f The Sew Astronomy, p. 197. 



by the bale-fires of their ruin ; but in a few cases its 

 actual relics come to hand. Those substantial enough to 

 escape total disintegration through atmospheric resistance 

 to their swift movements find their way to museums and 

 laboratories, where they are subjected to the searching 

 investigation demanded by their exotic origin. Its results 

 are scarcely what might have been expected. Meteorites 

 are not jjeculiar chemicallv : they consist exclusively of 

 the same elementary substances composing the crust of 

 the earth ; but their mineralogy is highly distinctive. 

 They are extremely complex structures, formed, apparently, 

 in the absence of water, and with a short supply of oxygen ; 

 the further condition of powerful pressure is indicated 

 with some probability, nav, with virtual certainty for those 

 including small diamonds ; * while prolonged vicissitudes 

 of fracture and re-agglomeration are possibly recorded by 

 the brecciated texture of many of these rocky trouvailles. 

 Their aspect is thus anything but primitive; each fragment 

 tacitly lays claim to an eventful history ; they suggest a 

 cataclysm, of which we behold in them the shattered 

 outcome. The nature of such cataclysms is scarcely open 

 to conjecture ; only a hint regarding it may be gathered 

 from the circumstance that the most profound terrestrial 

 formations are those which appn^ximate most closely to 

 the mineralogical characteristics of meteorites. 



Nevertheless, their only ascertained relationships are 

 with comets. In every system of shooting stars the 

 primary body most probably is, or at any rate was, 

 a comet. Each appears to be the offspring of a 

 cometary parent, and develops in the proportion of its 

 decay. The view has hence been adopted, and not without 

 justification, that comets in their primitive integrity are 

 simply ''meteor-swarms." Assent may be given to it with 

 some qualifications which we ueed not here stop to discuss. 

 What immediately concerns us is the interesting question 

 as to the constitution of meteor-swarms. What is the 

 real meaning of the term ? What does it convey to our 

 minds : A meteor-swarm may be defined as a rudely 

 globular aggregation of small cosmical masses, revolving, 

 under the influence of their mutual attraction, round their 

 common centre of gravity. Each must revolve on its own 

 account, though all have the same period ; and their orbits 

 maybe inclined at all possible angles to a given plane, and 

 may be traversed indifferently in either direction. From 

 this tumultuous mode of circulation collisions should 

 frequently ensue ; but they would be of a mild chai'acter. 

 They could not be otherwise in a system of insignificant 

 mass, and correspondingly sluggish motion. We are con- 

 sidering, it must lie remembered, only cometary swarms, 

 as being the only collections of the sort that come, even 

 remotelv, within our ken ; and comets include the minimum 

 of matter. None of those hitherto observeii. at least, 

 whether conspicuous or obscure, newly arrived from space, 

 or obviously effete, have occasioned the slightest gravita- 

 tional disturbance to any member of our system. 



Eventually, a cometary swarm, if left to itself, would 

 probably take something of a Saturnian shape. Colliding 

 particles would, owing to their loss of velocity, subside 

 towards the centre, and accrete into a globular mass. A 

 predominant current of movement would, through their 

 elimination, gain more and more completely the upper 

 hand ; and it would finally, with the inevitable diminution 

 of energy.t be restricted almost wholly to the principal 



* Carbon does not liquefy imder ordinary conditions. In the 

 production of his artificial diamonds. M. Moissan employed tremendoos 

 pressure and great heat ; but the genuineness of his products has 

 lately been denied. — Combes, iloniteur Scientifique, Xovember, 1903, 



t Sir K. Ball, "The Earth's Beginning," p. 243. 



