WHENCE CAME THEY.

Dominion, Volume 3, Issue 734, 5 February 1910, Page 10

WHENCE CAME THEY.

THE ORIGIN OF MBTEOEITES. 'Professor Pickering's analysis iff "Popular Astronomy*; of: the problem, of the meteorites elfectually disposes of some current beliefs and raises some, interesting points with regard to the erigin of these unheralded- visitors.., A' convenient classification' of .our that into siderites (iron alloyed with nickel), .aerolites (almost - wholly ;. ot stone); and 6iderolites (stone and _ iron in almost equal quantities). -To distinguish the'aerolite and the siderolite'from terrestrial. rock requires''somewhat close examination. The stony part of a meteorite is crystalline, and its ; structure :is what Gustav'Rose called "chondritic"— i.e., the loose grains form little spherules, chondroi or . chondres,; some' microscopio :and .others as large, as, a.'cherrystone: The chondritic formation is also to be found in .some terrestrial rocks—in,oo r ' for :instances-hut' with a (differ--erice'. The arrangement; of the fibres-in terrestrial' rocks- is as : tho .spokes •. of. a ' wheel, ■' diverging from a common: centre. This-is seldom the case with the meteorites, in which the arrangement is usually eccentric. 1 And there: is yet -a further mark of distinction. The chondres of: the terrestrial rocks are; not- 'of the' same material as'•: that: of .which the matrix .i5x..i0.rm.ed.,.,.. In the meteorites .the spherules are' of the ■ same'.-.composition as' the .matrix, and. of ten'..differ from the matrix only'in being more .coarselyi granular. >; - So' closely.-;in ' the-; popular mind are the/meteorites and falling stars allied' that:we. have,no- doubt that to -many 'theyVare.-.synonymous .terms.:' The connexion, • however, ceases to be clear: when v?e. apply.the. test of statistics, .The distribution', of,meteorites througHout; year can by no, means be reconciled with thaj;-of falling-stars and fireballs. We, have twice as;- many • falling Btars and fireballs- from July to December as. fron; January to; June.- With.'■ the meteorites, the case is-exactly:;the reverse.'--From' this Piofessbr.-Pickering'thinks we must infer that, while all meteorites are ■■ fire-, balls, perhaps^.;few. "■: fireballs ..'become, meteorites. "We must regard fiieballs oi rapid flight as allied,to the. falling stars, while among the meteors we must number such fireballs ;as move with comparatively. sl'o;y, velocities. -A very simple explanation; of the' 'meteorites would be. ..possible: if -wo '.could show that they have

been . expelled from the sun.. None. can . doubt, that' in ; the .past; there have, been' solar'". eruptions; of such; magnitude as., to ibejable to/.give' to,the meteorites'Veloci"tt'eslalan'.to those;of comets. Even then;it is difficult to why. the meteorites have'their orbits, of 'torday,' quite apart from'^hei' overwhelming-improbability/ of. the; assumption .that' solid l .stone or:iron ever, existed either oh .'the. surface of ..the sun or in its interior:: ■'. The early idea' that meteorites-we're';originally expelled 7 by: terrestrial : volcanoes, may. be' at once dismissed. -.We have -no reason to supposo that in.; prehistoric 'days :volcanic eruptions were of such'intensity as to be : able' ,to" give to a .projectile' a. .velocity which', ':even... at' -this; distance of, time, would be more; than;seven miles a second.. If of volcanic origin, could theyMje' pro-1 jectiles'from: the lunar mountains? -To this/ conjecture 'professor-. : Pickering re-1 ■ jiins that -no, explosive - volcanoes: have' ever* been' 1 detected on.the .moon's, surface, 1 s6:that:lunar;6rigiii.is, to say- the least of. it, 'highly, improbable/.'.- Next ,we come to Chamb«rHn's'/,theory, ac-. counting'.not only; for/meteorite3'.but. for comets shattered planetoids. |'IfiS>tKisi betjthe case, it ;is- diffc oult to; fact that, the fireballs originate have !ui'orbit n .quite .unlike .-that) of any <known ; comet;.jj-,To..sum L up,Valii,that is clear .is. i,th'at:'•iron:; and:-stony'.meteorites' differ-not.bnly.in;:their-composition but 'in other'ways as. well/:lt'seems plausible/ saysv the: American'astronomer, that some .of.the former are/associated .with falling stars,.and/therefore'with comets/ That some are-not- associated with: them seems probable. • Whence'' then, he asks, have tbey come,-;if not from ourownearth?— ."Westminster Gazette." .'-'."'. :,.-■-...-.'";.