Nearly fifty years ago, E. S. Dana published the sixth edition of the System of Mineralogy. While this book dealt almost entirely with the facts of mineralogy as known in 1892 and but little with theory, still it gives an excellent cross section of the science of that time. In what respects will a new edition of this work differ from its famous predecessor? As one of the group who has undertaken to prepare such a new edition and who has enlisted the help of this society in large measure for the necessary financial backing, I will undertake to present to you very briefly tonight some of the changes that must be recognized in the science of mineralogy after this half century of development.
No property of a mineral is so characteristic as its crystal form, and the science of crystallography, which attempts to describe and explain . . .