224 Dr. Walter Flight — History of Meteorites. 



iron = 25-59; iron oxide (fer oxyde) = 4-82 ; sulphur = 2-24; nickel 

 with trace of cobalt = 1-37 ; with traces of calcium, chromium, 

 manganese, arsenic, and phosphorus. Two points are worthy of re- 

 mark in this analysis : first, the astonishingly large amount of alumina 

 present, far in excess of that found in any other meteorite. In the 

 absence of a second and confirmatory analysis, it may be assumed 

 that insufficient ammonium chloride was employed, and the greater 

 portion of the 16*84 per cent, is magnesia, which was precipitated 

 with the alumina. Secondly, the occurrence of arsenic, which is of 

 extreme rarity, in a meteorite ; it is stated to be present in the 

 iron of Braunau and the olivine of the Atacama siderolite. 



Tschermak's report of his examination of this stone appeared in 

 the winter of 1874. The structure developed on cutting the stone is 

 unusual and remarkable, consisting of light- coloured fragments (I.), 

 surrounded by a compact dark cementing material (II.). The former 

 are yellowish-grey, inclose spherules and particles of iron and 

 magnetic pyrites ; are, in fact, normal chondrite, and resemble the 

 mass of the stone which fell at Seres in Macedonia (1818, June). 

 The latter incloses numerous particles of iron and magnetic pyrites, 

 for the most part uniformly distributed ; the portion nearest the 

 inclosed fragments bears very distinct indications of having been at 

 one time fluid, and conveys the impression that this cementing 

 material was at one time in a plastic condition while in motion. 

 Along the boundary of these two very dissimilar portions flaws are 

 seen, in which nickel-iron has crystallized in delicate plate-like 

 forms ; and here, moreover, the fragments are darker, harder, and 

 more brittle than those of the centre, which argues the exposure of 

 the cementing material to a very high temperature while in a plastic 

 condition. Both portions have nearly the same density and appar- 

 ently the same chemical composition and mineral characteristics. 

 The Orvinio stone resembles, in fact, certain brecciated volcanic 

 rocks which consist of a ground mass through which granular frag- 

 ments of the same rock are distributed, as when older crystalline 

 lavas are interpenetrated by others more compact and of a more 

 recent period. 



The light-coloured fragments are, as has been stated, chondritic ; 

 the spherules are usually of one kind, lying in a splintery matrix of 

 the same mineral, containing some nickel-iron and magnetic pyrites. 

 Among the transparent constituents, olivine is recognized by its im- 

 perfect cleavage ; a second mineral, with a distinct cleavage along 

 a prism of nearly quadratic section, is evidently bronzite ; while 

 a third, which occurs in fine foliated or fibrous particles, may be 

 either identical with the above or be a felspathic ingredient. 



The meteoric rocks possessing chondritic structure are regarded 

 by Tschermak as tufas, which have undergone detrition ; and their 

 spherules to be such particles as, by their superior toughness, have, 

 during the trituration of the rock, instead of breaking up into 

 splinters, acquired a rounded form. 



A black material is observed to coat the fragments of the rock 

 and to fill the finer flaws existing between them, whereby their 



