03 May 1974
Vol 184, Issue 4136

About The Cover

Rare-earth fersmite spherulite in matrix of metamict polycrase viewed in transmitted light under crossed polars. The spherulite is approximately 80 micrometers in diameter. Although individual fibrils are barely visible, the anisotropic, birefringent spherulite contrasts with the surrounding isotropic metamict polycrase. The birefringence of the spherulite increases toward the center region. See page 561. [Rod Ewing, Stanford University, Stanford, California]