THE AGE OF THE EARTH
      by G. Brent Dalrymple
      Stanford University Press  1991
      QE508.D28  1991  551.1--dc20  90-47051 CIP
      ISBN 0-8047-1569-6


      LAND NAVIGATION HANDBOOK
      The Sierra Club Guide to Map and Compass
      by W. S. Kals
      Sierra Club Books  1983
      GV200.4.K34  1983  796.5  82-16917
      ISBN 0-87156-331-2


      THE AGE OF THE EARTH is a definitive, masterly history and synthesis of
      all that has been said (by theologians and scientists) and is known (to
      science) about the question, How old is the Earth? It explains in a
      simple and straightforward way the evidence and logic that have led
      scientists to conclude that the Earth and the other parts of the solar
      system are not several thousand years old, as some today would have it,
      but four and one-half billion years old.

      It is a fascinating story, but not so simple as a single measurement.
      Our universe is a large, old, and complicated place. Earth and other
      bodies have endured a long and sometimes violent history, the events of
      which have frequently obscured the record that we seek to decipher.
      Although in detail the journey into Earth's past requires considerable
      scientific skill, knowledge, and imagination, the story is not so
      complicated that it cannot be explained to someone who wants to know and
      understand the basic evidence. This book, then, has been written for
      people with some modest background in science, but at a level that will
      allow the material to be useful and accessible to those without a deep
      knowledge of geology or physics or mathematics.

      Most of the book is organized into chapters that discuss the several
      types of evidence for the age of the Earth. The first two chapters give
      a brief history of the universe as science knows it and an account of
      some of the historical attempts, made before modern radiometric methods
      were realized, to determine the age of the Earth. The quantitative
      evidence for Earth's are is based on measurements involving long-lived,
      naturally occurring radioactive isotopes, and Chapter 3 explains how
      these methods work and how they can be used to date events that occurred
      so far back in the distant past.

      Chapter 4 is a discussion of the Earth's oldest known rocks. It may
      surprise some readers to learn that the first 700 million years or so of
      Earth's history have been effectively erased, and that the oldest rocks
      found on Earth are not nearly so old as the Earth itself. Some of the
      key evidence for the age of the Earth comes from bodies in the Solar
      System that are less highly evolved. These bodies, the Moon and
      meteorites, provide a record of the timing of some of the earliest
      events in the Solar System, and the ages of the oldest lunar samples and
      meteorites are the subjects of chapters 5 and 6.

      Chapter 7 explains the simple and elegant method that provides us with a
      reasonably accurate figure for the age of the Earth, and Chapter 8
      discusses the evidence for the ages of the Milky Way Galaxy and the
      Universe. The final chapter summarizes what we know and would like to
      know about the age of the Earth.



      Every out-doorsperson (and every grazing-star-occulter) at one time or
      another needs to chart a course in the wilderness. In LAND NAVIGATION
      HANDBOOK an expert navigator, W. S. Kals, combines his map-and-compass
      skills with a special concern for the needs of the wilderness wanderer
      to create a comprehensive primer for the beginning pathfinder and the
      veteran woodsman. Kals, a former planetarium director, is author of
      PRACTICAL NAVIGATION and THE STARGAZER'S BIBLE, among other books.

      Not only do you learn how to navigate from the sky anywhere on the
      planet, but you also learn how to find out where you are--essential for
      many an astronomical calculation. Kals' subject matter includes:
      Choosing and using a compass; Reading topographic maps; Measuring
      distances and estimating travel times; Determining and adjusting for
      local declination around the globe, including allowances for annual
      change; Altimeter navigation; Navigation using the sun and stars,
      including instructions for the tropics and southern hemisphere. After
      recently reading half a dozen books dealing with land navigation, this
      reviewer finds Kals' book is the most readable, informative and useful.


                                                              -S. Wormley