MICROSCOPIC IDENTIFICATION OF CRYSTALS.

By Richard E. Stoiber '32(Frederick Hall Professor of Mineralogyand Chairman of Department of EarthSciences) and Stearns A. Morse '52. NewYork: The Ronald Press, 1972. 278 pp.$10.50.

Early in the 19th century the development of the polarizing microscope touched off an avalanche of discoveries on the innate properties of crystals, which continues today in studies ranging from neutron diffraction to infra-red spectroscopy. The heyday of research in crystal optics may be passed, yet a knowledge of the optical properties of crystals is still essential to understanding the many varieties of modern spectral analysis.

As a practical tool the polarizing, or petrographic, microscope continues to have important applications. In a time when so many data are obtained indirectly with complex machines this relatively simple and inexpensive device permits direct and useful observations of the nature of crystalline materials. With a polarizing microscope, for example, the major element concentrations in thousands of inorganic and organic substances can be quickly and reliably estimated. So it is a fine thing that Professor Stoiber and Mr. Morse, Associate Professor of Geology at the University of Massachusetts, have written a text on optical crystallography and the use of the petrographic microscope.

Dartmouth geologists will recognize the book as a revised edition of the trusty old pumpkin, an orange-covered paperback which Professor Stoiber wrote and used in his courses for many years. The cover is still Agfa-box orange, but inside the pumpkin is much changed. I have carried my copy of the old edition round the world. Each time I opened it I could hear Dick's frenzied voice in the text: "Becke line in, crystal high!", and this voice sustained me through many tedious refractive index measurements. Well, the words are still there, but the voice is gone. I'm not certain why; perhaps the combination of more polished prose, influenced by Professor Morse, handsome letterpress, and halftone illustrations has come between me and the voice of my friend, LeRoc Docteur. So be it. The book is greatly improved. Students at Dartmouth and elsewhere will find it a lucid and straightforward introduction to the study of crystal optics.

Mr. Dickey is Assistant Professor of Geol-ogy, Department of Earth and PlanetaryScience, Massachusetts Institute of Technol-ogy.