Lead, Platinum, and Other Heavy Elements in the Primary Cosmic

From an analysis of ?8~ days of exposure of the Heavy Nuclei Experiment on the HEAO 3 spacecraft, we have selected 322 nuclei with reasonable charge resolution, E ;;::::: 1.3 Ge V n1 and Z ;;::::: 50. These data show a defined ~b~ndance peak in the "platinum" (74 ~ Z ~ 80) region, a small abundance of" lead" (81 ~ Z ~ 83), and a sigmfica~t num~,e~ o~ "_secondary" nuclei in the ~2 ~ Z ~ 73 range. The deduced ratio in space of 0.25 ± 0.09 for Pb/P.t IS distmctly lower th~n that predicted by any of the standard models for cosmic-ray sources and propagatiOn effects. Although this low ratio suggests an enrichment in the cosmic-ray source of products of r-J?roce~s nucleosynthesis, it may_ rather be an indication that the Pb abundance is suppressed by a source fract10nat10n effect, or that there IS less Pb in the solar system than is assumed in the standard