COMPOSITION AND STRUCTURE OF METEORITES 35 



Other grains occur with a fan-shaped arrangement of crystalline needles, which an 

 uncautious, nonmicroscopical observer might counfound with simple concretions. 

 They have, however, a structure entirely different from any concretions met with 

 in terrestrial rocks, as for example, that of oolitic grains. In them we often see a 

 well-marked nucleus, on which radiating crystals have been deposited equally 

 on all sides, and the external form is manifestly due to the growth of these crys- 

 tals. On the contrary the grains in meteorites now under consideration have an 

 external form independent of the crj'stals which do not radiate from the center, 

 but from one or more places on the surface. They have, indeed, a structure 

 absolutely identical with that of some artificial blowpipe beads which become 

 crystalline on cooling. With a little care these can be made to crystallize from 

 one point, and then the crystals shoot out from that point in a fan-shaped bundle, 

 until the whole bead is altered. 



In this case we clearly see that the form of the bead was due to fusion, and 

 existed prior to the formation of the crystals. The general structure of both of 

 these and the previously described spherical grains also show that their rounded 

 shape was not due to mechanical wearing. Moreover, melted globules with 

 well defined outline could not be formed in a mass of rock pressing them on all 

 sides, and I, therefore, argue that some at least of the constituent particles of 

 meteorites were originally detached glassy globules, like drops of fiery rain.^" 



In this Sorby would appear to have had reference only to "kugels" 

 with radiate, internal structure. 



Tschermak, who together with Haidinger, was one of the first to 

 pronounce on the tuff-like character of the chondritic meteorites, 

 announced in 1874 ?'^ the opinion that the individual chondrules 

 (kugelchen) were but rock particles which became simply rounded 

 under conditions similar to such as might exist in the throat of a 

 terrestrial volcano. 



Ich wiederhole hier nur das Eine, dass Ich die Chondrite fur Zerreibungs-Tufe, 

 und die Kugelchen derselben fur solche Gesteinspartikelchen halte, welche 

 wegen ihrer Zahigkeit bei dem Zerreiben des Gesteines nicht in Splitter aufgelost, 

 sondern, abgerundet wurden. 



And again in 1875:^^ 



Man kann sich allenfaUs vorstellen dass die Steinmassen, welche der Zerrei- 

 bung ausgesetzt waren, ziemlich weich gewesen seien und wiirde sich dadurch der 

 Vorstellung Daubrees nahern, welcher an ein Gestein denkt, welches in einer 

 Gasmasse wirbelnd erstarrte; doch ist es sicher, dass die Kugelchen das Resultat 

 einer Zerreibung sind. 



69 Sorby's idea, as it seems to the author, may be visualized and made probable by a consideration of a 

 meteorological phenomenon common during the winter months in cold latitudes. It not infrequently 

 happens that on the occasion of a cold winter storm, owing to meteorological conditions, the snow (con- 

 densed water vapor) falls not in the customary form of flakes, but in that of hard, icy pellets of approximate 

 pin-head size, comparable with a chondrule. In a cold, dry atmosphere and with a high, intermittent 

 wind, these particles are driven at a great speed in all directions through the air, constantly colliding with 

 one another and ultimately reaching the ground, where, under the same influences they are drifted over the 

 surface, still colliding with one another and the various obstructions, until an ever variable proportion 

 of them are shattered or disintegrated— finally coming to rest to be compacted in a more or less solid mass 

 comparable with that of the more friable chondritic meteorite stones. The theory, it will be observed, 

 thus accounts for the origin of the chondrule as well as that of the stone itself. 



~o Die Trummerstructur d. meteoriten, etc., Sitz. k. Acad. Wiss., Wien., vol. 70, 1874, (4). 



" Idem, vol. 71, 1875. 



