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<p><span style="color: rgb(33, 37, 41); font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", "Liberation Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji"; letter-spacing: 0.7px;">The first edition of this book, a slender volume of 128 pages written by the late Dr F. H. Hatch, O.B.E., was published in 1891. In 1926 one of us (A.K.W.) joined Dr Hatch in a complete revision. In the tenth edition another of the main props of former classifications-silica percentage - was discarded in favour of the mineral contents of the rocks. As might be expected, the subject matter and illustrations of the original book have through successive editions been completely replaced. The descriptions of minerals are especially tailored for use in the practical study of igneous rocks, and as such form an integral part of the whole book without which we, believe much of the value of the petrographical and petrological parts of the text would be lost. Since the last edition was published in 1961, fundamental advances have been made in understanding the nature of the major structural features of the Earths crust, and of the role of igneous activity in their development. The significance for petrology of modern concepts in global geophysics and geology is recognized by the inclusion of a new chapter on the geological setting of igneous activity.</span><br></p>
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