452 
PETROLOGY: G. P. MERRILL 
Proc. N. a. S. 
meteorites of Elm Creek, Hessle, and Parnallee. The mineral in all cases 
is enstatite^ and the outline of the spherule as sharp and clean as though 
it had been turned on a lathe. In the Elm Creek example crystallization 
FIG. 3 
evidently began at one point on the surface of the spherule and extended 
inward throughout, but the cooling proceeded too rapidly for the produc- 
tion of an optically perfect crystal. In the Hessle stone (fig. 4), there 
were evidently several initial points of crystallization. Forms like these 
FIG. 4 
grade imperceptibly into such as are shown in figure 5, in which the radi- 
ating bars have unmistakably the crystallographic properties of enstatite. 
II. Half Glassy, Barred and Porpkyritic Forms. — Porphyritic forms are 
