SUPPLEMENTARY NOTE 55 



ing to conditions. In reality the reverse is the case, the chon- 

 drules being more or less glassy, or at least imperfectly crys- 

 talline, as in the barred and fan-shaped forms, while the 

 groundmass of the rock is of crystalline particles, and of parti- 

 cles of the chondrules themselves. So far as I have observed 

 there is no true glassy base in meteorites of this type. 



That certain conditions of crystallization will give rise to the 

 spherulitic forms of the enstatite is undoubted, but from a study 

 of the crust of the Allegan stone it appears that when meteoric, 

 material is fused and allowed to re-crystallize, even so rapidly 

 as must have been the case in this crust, it is not spherulitic, 

 but takes the form of crystallites in a glassy base, as among 

 terrestrial rocks. It is evident that time is not the only factor 

 that should be considered. 



The subject of the spherules in liparite has been pretty well 

 worked out by Cross and Iddings,^ and while it is easy to con- 

 ceive of the abrupt transition from a wholly or partly crystalline 

 spherule to a glassy base, as sometimes seen in 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 crys- 

 talline particles, shown in many meteorites. Even could we 

 account for such anomalies of crystallization as are above noted, 

 the presence of plainly fragmental chondrules — chondrules 

 which were fragments at the time of the final consolidation of 

 the stone — remains to be explained. The forms shown in PL 

 IV were all carefully picked from the rock. That they are 

 original fragments, i. e., not due to fracturing in place, is shown 

 by the dull and sometimes abraded character of the surface of 

 fracture, and further by the fact that in no case was the re- 

 mainder of the chondrule represented by one of these pieces 

 found in the vicinity. Fig. 6 of this plate is one of the most 

 striking illustrations of this nature, being that of a portion of an 

 oval enstatite chondrule some 8 mm. in greatest diameter, im- 

 bedded in a fine granular groundmass. The flat surface of 

 fracture is dull and lusterless, and the fracture is, I believe, 

 unquestionably an old one. Fig. 7 shows a side view of the 



1 Bull. Phil. Soc. Washington, Vol. XI, 1891. 



