Contents

20 October 1972
Vol 178, Issue 4058

About The Cover

Fission track sunbursts from dust particles record the uranium concentraron and size of the particle. The tracks are from fission induced by irradition of a dust particle on a piece of mica and are revealed by chemically etching the mica in hydrofluoric acid (about X 2200for background; X 750 for insects). See page 255 [P B Price and R.M. Walker,Jurnal of Geophysical Research, 68,4847 (1963)]