32 



KNOWLEDGE 



[February 1, 1899. 



no "new geology," any more than there is a new heaven 

 or a new earth. In this, as in other sciences, the great 

 discoverer is preceded in his triumph by the veteran legions 

 who have seen more service than himself. The records of 

 patient labour, sometimes laid aside owing to their obvious 

 incompleteness, the work of men in candle-lit laboratories, 

 or in mining camps among the mountains, may at length 

 receive their interpretation, and fall into their place in the 

 great argument of reason. Everywhere these friendly 

 linkings with the past provide new stimulus for research ; 

 and it is not always the young and undefeated who sound 

 the reveil upon the field. 



I.— THE UNSEEN CORE. 



The public mind has always been impressed by the fall 

 of strange bodies upon the earth, sometimes from our own 

 atmosphere, sometimes from outer space. " Red rains," 

 regarded as showers of blood, have been held to presage 

 deadly evils ; and the descent of small frogs, or even fresh- 

 water fishes, has been looked on as a dubious blessing. 

 The explanation that red mud, and the accessory frogs, 

 may be carried up from drying pools by whirlwinds, and 

 that the contents of crater-lakes may be flung broadcast by 

 volcanoes, has hardly allayed popular suspicion. Still 

 more impressive have been the records of the fall of 

 meteoric stones, at times accompanied by the flash of a 

 visible meteor. The tradition of such occurrences was, in 

 old time, passed from one hearer to another, and even 

 ordinary lightning became credited with an accompanying 

 " thunderbolt." Concretions of metallic ores, such as the 

 marcasite nodules of the chalk, are even now pointed to as 

 " thunderbolts " ; and this fact, based on their superficial 

 resemblance to true meteorites, shows that the latter must 

 have been observed with tolerable frequency. Meteorites 

 that had actually been seen to fall were, naturally enough, 

 accounted precious and miraculous, and were occasionally 

 preserved in churches. In still more ancient days they were 



objects of worship, 

 and were associated 

 with recognised 

 divinities, such as 

 Diana of the Ephe- 

 sians. The philoso- 

 phers of the Renais- 

 sance, however, swept 

 aside a number of 

 valuable traditions, in 

 their very pardonable 

 zeal, and they re- 

 fused to believe that 

 meteoric masses could 

 reach our planet from 

 without. Gassendi, 

 who saw a meteorite 

 fall in Provence in 

 1627, thus attributed 

 it to some unknown 

 terrestrial eruption ; 

 though a mass of 

 fifty-nine pounds, 

 descending in proud 

 isolation on the soil 



Fl&. 1.— Cut surface of Meteorite 

 (Spoiadosiderite) wliich fell at Mocs, 

 Kolozs, TrausylTania, 3rd Feb., 1882. 

 X 12. Bright irregular specks of nickel- 

 iron lie scattered in a ground consisting 

 mostly of basic silicates. One of the 

 globular '*chondroi" shows as alight- 

 coloured circular ai-ea in the section. 

 (From a specimen in the Eoyal 

 College of Science for Ireland ) 



of France, surely deserved further consideration. 



It was left for Chladni, in 179-1, to revive, on scientific 

 grounds, the well-founded belief of older days. He particu- 

 larly commented on the mineralogical peculiarity of the 

 " Pallas Iron," a huge block of nickel-iron and included 

 olivine, found in Siberia in 1749. This appeared to him 

 not to resemble any known terrestrial material, In the 



same belief, Sir Joseph Banks collected specimens from 

 Siena. (1794), Yorkshire (1795), and Benares (1798), and 

 submitted them to Mr. Edward Howard. Aided by the 

 Comte de Bournon, Howard published the first truly scien- 

 tific report on " certain stony and metallic Substances 

 which at different Times are said to have fallen on the 

 Earth ; also on various Kinds of native Iron." ''■'• Nickel 

 was here recognised as a constituent of the iron masses ; 

 and Howard, while offering no conclusion, clearly inclined 

 towards the meteoric view. When an idea has been 

 denounced as superstition, it is slow to come again into 

 favour ; but the fortunate fall of stones at I'Aigle, in 

 Normandy, in 1803, gave the French Academy an oppor- 

 tunity of forming an independent opinion. Blot's report 

 converted those who sent him into the field ; and the 

 genuineness of the fall of stones " from heaven " has not 

 been questioned subsequently.! 



Among the meteoric stones investigated from time to 

 time, a number were found to consist of metallic iron, with 

 some five or ten per cent, of nickel. Only a dozen or so 

 of these iron meteorites have actually been seen to fall, 

 including one near the Wrekin in 1876 ; but many other 

 conspicuous masses, found lying on the surface of the earth, 

 have been assigned a meteoric origin, on account of their 

 resemblance to specimens about which there is no manner 

 of doubt. One of the striking features of many such irons 

 is the development of characteristic figures when a polished 

 surface is etched with nitric acid. Von Widmanstetter 

 (also known as von Widmanstatten) observed these as early 

 as 1808 ; and it has since been shown that the systems 

 of crossing bands and lines are due to the varying degree 

 of resistance of different alloys of nickel and iron. In the 

 most easily attacked layers, there may be fourteen parts of 

 iron by weight to one of nickel ; in the most resisting parts, 

 which remain as thin bright streaks above the dull etched 

 areas, the proportion of iron to nickel may be only six to 

 one. The bands thus developed on a polished surface are 

 usually the edges of four sets of layers grouped parallel to 

 the faces of an octahedron, and represent successive zones 

 or stages in the growth of the crystalline mass. The iron 

 particles ^contained in some stony meteorites are much 

 richer in nickel than are the ordinary iron meteorites ; 

 which proves that highly nickeliferous ores may yet some 

 day descend in mass from space. Indeed, the material 

 from the province of Santa Catharina, in Brazil, with 

 68-69 per cent, of iron, and 33-97 per cent, of nickel, and 

 that from Octibbeha, Mississippi, with 37-69 per cent, of 

 iron, and as much as 59-69 per cent, of nickel, are com- 

 monly regarded as truly meteoric. 



All these iron masses, ranging from mere pebbly particles 

 up to blocks measuring several feet across, present striking 

 differences from the ordinary materials of the earth's 

 crust. Metallic iron is one of the least important con- 

 stituents of the rocks to which we readily have access. 

 Even now, it has not been recognised as a common 

 mineral, though it may occur in the form of minute grains 

 in a number of basic igneous rocks. The iron familiar to 

 us in analysis, which forms, according to Mr. F. W. Clarke, 

 some five per cent, by weight of the earth's crust, occurs 

 as the oxides (magnetite, hematite, or limonite), as the 

 sulphides (pyrite, marcasite, and pyrrhotine), as the car- 

 bonate (siderite), or shut up in combination in a variety of 

 common silicates. 



Terrestrial native iron, however, has long been re- 

 ported from the platiniferous sands of Brazil, not to men- 



* PMl. Trans. Roy. Soc, 1802, pt. i., p. 168. 



-)• See L. Fletcher, " Introduction to the Study of Meteorites," issued 

 ' ■ as a guide-book at the British Museum. 



