. Guide leaflet. ianstatten hnos. Another group of iron meteorites, com-posed of homogeneous masses of nickel-iron, show cleavage and lamellae parallelto the faces of a hexahedron. This is due tothe twinning of a cube on an octahedralface. On etching with dilute nitric acidthe structures show Neumann lines. Suchforms are known as hexahedral irons. A third group of irons are called massiveirons or ataxites because their structure isamorphous and shows neither Neumann orWidmanstiitten lines or other pronouncedfeatures. The structure of the aerolites is quitedifferent. They resemble the light col
. Guide leaflet. ianstatten hnos. Another group of iron meteorites, com-posed of homogeneous masses of nickel-iron, show cleavage and lamellae parallelto the faces of a hexahedron. This is due tothe twinning of a cube on an octahedralface. On etching with dilute nitric acidthe structures show Neumann lines. Suchforms are known as hexahedral irons. A third group of irons are called massiveirons or ataxites because their structure isamorphous and shows neither Neumann orWidmanstiitten lines or other pronouncedfeatures. The structure of the aerolites is quitedifferent. They resemble the light coloredfelsitic rocks of the earths crust, but theyare unlike them. Aerolites may be granu-lar, crystalline, chondritic, basaltic, tuff-like or breccia-like and with or withoutveins. Metallic shreds may or may notbe scattered through the mass. While thecolor is usually light gray, it may varythrough various shades of gray to characteristicfeature of aero-lites is that whiletheir interiors maybe gray in tone,. with various chondrules or mineralgrains in evidence, their exterior surfacesare always coated with a thin blackcrust, which varies in thickness from %4to }-s2 of an inch. Astronomers tell us that about 400,-000,000 celestial objects enter the earthsatmosphere every day, that about 20,000,-000 are large enough to form shootingstars or meteors, and that of this number aminimum of but one per day is of sufficientsize to reach the earth and constitute ameteorite. At first it may seem strangethat so many meteors enter the atmos-phere and so few reach the earth. Whenit is recalled, however, that meteoritesvary from sizes microscopic to objectsmeasured in tens of cubic feet, that theyenter the upper rarefied layers of theearths atmosphere at speeds varyingfrom 8 to 50 miles per second, and thatthe atmosphere offers great resistance totheir passage, it is not surprising that inthe few seconds of their flight through theatmosphere that most of them are heatedto the point ofin
Size: 1345px × 1859px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectnatural, bookyear1901
