Differentiation in Silicate Liquids. 



181 



In spite of the fact that the charges were very much cracked 

 by the sudden chilling, it was possible in some cases to make a 

 vertical section by grinding down the whole charge. One of 

 these is shown in "fig. 3. The black border of irregular width 



Fig. 





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Fig. 3. Vertical section of crucible showing pyroxene crystals in glass, 

 x 5. 



bounding the sides and bottom is the remnant of the platinum 

 crucible left after grinding. The surface of the liquid is 

 marked by a line of amphibole crystals (principally spherulites) 

 which formed at the surface during cooling in spite of the fact 

 that this was very rapidly accomplished. The surface of the 



