20 BULLETIN 9i, UNITED STATES NATIONAL MUSEUM. 



mass of the stone is of crystalline particles and of particles of the 

 chondrules themselves. 



That certain conditions of crystallization would give rise to spher- 

 ulitic forms of the enstatite is undoubted. The subject of their 

 development in liparite has been worked out by Cross and Iddings,^ 

 and while it is easy to conceive of the abrupt transition from a wholly 

 or partly crystalline spherule to a glassy base, as sometimes seen in 

 the spherulites of obsidian, it will, in the present state of knowledge, 

 puzzle any petrographer to account for an equally sharp transition 

 from a glassy spherule (chondrule) to a base composed wholly of 

 crystalline particles, as shoAvn in many meteorites. Even could one 

 account for such anomalies of crystallization as these, the presence 

 of plainly fragmental chondrules— chondrules which were fragments 

 at the time of the final consolidation of the stone— would still re- 

 main to be explained. That many of the chondrules in this stone 

 were the results of earlier fracturing is shown conclusively by the 

 dull and abraded character of the fractured surface. With reference 

 to the porphyritic forms in the glassy and fibrous ground, shown by 

 some of the chondrules, one can assume that after the phenocrysts 

 had become secreted the magma was resolved into spherical drops 

 which cooled too rapidly for further crystallization, while in the 

 radiated forms crystallization may have taken place in some cases 

 prior to the assumption of the globular form, and in some subsequent 

 thereto. Such forms lend support to the theory of Sorby, already 

 quoted. It is possible to conceive that these, first as blebs of molten 

 matter and then as consolidated particles, may have been triturated 

 in the deep throat of some volcano. The spherical form, however, is 

 not regarded by the present writer as due to trituration like volcanic 

 lapilli, but rather to a previous molten condition. While it may be 

 possible to account for the present condition of the chondritic meteor- 

 ites, as regards degree of consolidation, on the theory that they are 

 tuffs more or less metamorphosed by high temperatures, the chon- 

 drules can not themselves be thus accounted for, since a heat sufficient 

 to render crystalline the pisolites in a tuff, as argued by some, would 

 certainly produce a more marked degree of metamorphism in the sur- 

 rounding matrix. There is apparently no escape from the idea that 

 so far as the spherical chondrules are concerned, they are independ- 

 ently formed, though, it may be, greatly corroded and mechanically 

 abraded prior to their ingathering into the stony masses coming to 

 earth from space. That many of the external forms now presented 

 are due to mechanical causes is self-apparent, and it is possible that 

 not all have a common origin. 



Other structural features. — The position occupied by the metallic 

 constituent in a stony meteorite or pallasite is such as to indicate 



»Btill. PMIos. Soc. Washington, vol. 11, 1891. 



