ty of a man named Bill Compston,  in t t Sensitive ion Ion MicroProbe—or S is more affectionately knos initial letters. t measures te of uranium in tiny minerals called zircons. Zirconsappear in most rocks apart from basalts and are extremely durable, surviving every naturalprocess but subduction. Most of t o t somepoint, but just occasionally—in estern Australia and Greenland, for example—geologistscrops of rocks t  ton’s maco be dated otype Sand macment’s os on a budget, but it . On its first formal test, in1982, it dated t ternAustralia.

    “It caused quite a stir at time,” Bennett told me, “to find sometant soquickly echnology.”

    Sook me doo see t model, S eel apparatus, per long and five feet  asa deep-sea probe. At a console in front of it, keeping an eye on ever-crings offigures on a screen, erbury University in Ney-four many rocks to date. It  after 9A.M. and Bob ill noon. Ask a pair ofgeocs art talking about isotopicabundances and ionization levels  is more endearing thomable.

    t of it,  treams of coms, is able to detect subtle differences in ts of lead anduranium in tely adduced.

    Bob told me t it takes about seventeen minutes to read one zircon and it is necessary toread dozens from eaco make ta reliable. In practice, toinvolve about ttered activity, and about as mucimulation, as a trip to alaundromat. Bob seemed very  then people from New Zealand verygenerally do.

    tion of t offices, part labs,part maco build everytt said. “e even  ire