SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 143, NO. 4, PLATE 4 



A, B, Photomicrograph of a 0.25-cm. slice of Martha's Vineyard tek- 

 tite, X 10. A, White transmitted light ; B, crossed nicols. 



C, D, Photomicrograph of a 0.07-cm. slice of the Empire, Ga., tektite, 

 X 10. C, White transmitted light; D, crossed nicols. 



