ded rocks t remely ancient, containing lead- and uranium-bearing crystals t  as old as t itself—anytes—but really ancient rocks are only rarely found on Earte 1940s no onealtogetood o t for e tectonics, o.) Patterson,meantime,  to try to make sense of ted materials. Eventually, andingeniously, it occurred to   tage by using rocksfrom beyond Earturned to meteorites.

    tion  correct as it turned out— manymeteorites are essentially leftover building materials from tem,and to preserve a more or less pristine interior cry. Measure th.

    As alraigionmakes it sound. Meteorites are not abundant and meteoritic samples not especially easy to get tecreme andneeded muc. Above all, t Patterson’s samples inuously and unaccountably contaminated mospo air. It  eventually led o create a sterile laboratory—t, according to at least one account.

    It took Patterson seven years of patient  to assemble suitable samples for finaltesting. In traveled to tional Laboratory in Illinois,ime on a late-model mass spectrograpectingand measuring te quantities of uranium and lead locked up in ancient crystals.  last s, Patterson ed t raigo o a al because   attack.

    Soon after a meeting in isconsin, Patterson announced a definitive age for t standsuncer,” as McGrayne admiringly notes. After th finally had an age.

    terson nourned tention to tion of all tlead in tmospounded to find t tle  tsof lead on  invariably  surprisingly, y years every study of lead’s effects urers of lead addit