THE STRUCTURE OF METEORITES 63 



present supposed number will doubtless be further reduced by care- 

 ful study since some accredited meteorites will be found to be arti- 

 ficial irons and others will give Widmanstatten figures on further 

 treatment. The true ataxites resemble ordinary cast iron in struc- 

 ture. There are sometimes variations in a single mass from a com- 

 pact homogeneous structure to one of a coarse grained character. 

 Several show indistinct broad bands and others a sheen (Eise?i- 

 mohr, moire metallique} on etching. Inclusions of graphite, phos- 

 phides and sulphides of iron (such as schreibersite, troilite, etc.) 

 occur as in the octahedral irons. Unusually high content of 

 nickel characterizes some, while others have an average com- 

 position. On the whole the ataxites may be said to form an 

 anomalous and little understood group. 



2. Stone meteorites. — No stone meteorites are amorphous in 

 structure as a whole ; only the ground mass is sometimes found to 

 be of this character. In some cases a ground mass appearing 

 amorphous is found in reality to be made up of consolidated frag- 

 ments of dust-like minuteness. In other cases, as in the stones of 

 Richmond and Goalpara, the ground mass is really semi-glassy 

 and unindividualized. The ground mass of most of the carbona- 

 ceous meteorites is of a black unindividualized character, and 

 appears closely allied to the substance to be described later as 

 forming veins. In the brecciated stones of Orvinio and Chan- 

 tonnay a black ground mass cements the fragments of chondritic 

 texture together and exhibits a distinct flow structure about 

 them. A brown glass is also found cementing together some of 

 the crystalline and tuffaceous meteorites. 



BRECCIATED STRUCTURE. 



This is of rather common occurrence. According to Wulfing's 

 classification it characterizes meteorites of sixty-two falls. Brec- 

 cias occur both of the type of angular fragments compressed 

 together and of angular fragments imbedded in a ground mass 

 which may have been at one time in a fused or pasty condition. 

 Among the iron meteorites the fragments are largest in the Mt. 

 Joy meteorite. The contour of each of these is so distinct that 



