253 KEPORT — 1875. 



and acid 45-04 per cent. The analysis of a portion of the stone gave 

 the following numbers: — silicic acid=4G-72, alumina = 16'S4, magnesia 

 = 1-07, iron=25-59, iron oxide {fer oxide)= 4-S2, sulphur = 2-24, nickel 

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

 arsenic, and phosphorus. Two points are worthy of remark in this analj'sis : 

 hrst, 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 cm- 

 ployed, and the greater portion of the 1G-S4 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 he present in the iron of 

 Braunau and the olivine of the Atacama siderolito. 



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 re- 

 markable, consisting of light-coloured fragments (I.), surrounded by a compact 

 dark cementing material (II.). The fonner arc yellowish grey, enclose sphe- 

 rules and particles of iron and magnetic pyrites, are, in fact, normal chon- 

 drite, and resemble the mass of the stone which fell at Seres, in Macedonia 

 (1818, June). The latter encloses numerous particles of iron and magnetic 

 pyrites, for the most part uniformly distributed ; the portion neai'est the en- 

 closed fragments bears very distinct indications of having been at one time 

 fluid, and convcj's the impression that this cementing material was at one 

 time in a plastic condition while in motion. Along the boundary of these two 

 very dissimlar 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 con- 

 dition. Both portions have nearly the same density and apparently the same 

 chemical composition and mineral characteristics. The Orvinio stone re- 

 sembles, in fact, certain brccciated volcanic rocks, which consist of a groimd- 

 mass through which granular fragments 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 sphe- 

 rules 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 imperfect cleavage ; a second mineral, 

 Avith 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 arc regarded by Tschcr- 

 mak as tufas which have undergone detrition, and their spherides 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 transparent character 

 is considerably impaired ; this has also been noticed in the meteorite of Tad- 

 jcra (1867, June 9th). 



The dark-coloured cementing material contains two ingredients : an opaque 

 semivitreous constituent, and particles in every way similar to the dark crust 

 of the fragments from which they may probably have been detached ; many 

 of them can still be recognized as olivine and bronzite. The nickel-iron and 

 magnetic pyrites of this portion of the stone are more finely divided than 



