This book presented, for the interested, and educated, public, a summary of the method invented by William H. Bragg and his son, William L. Bragg (Nobel prizes, 1919) by which one could, with relative ease, and access to the appropriate equipment, determine the crystal/atomic structure of most common crystals. This work, along with the work of others (which can be obtained by searching for "x-ray diffraction history". The value of the Braggs method lies in its simplicity. Sir W.H. Bragg discusses their application of the geometric methodology of reflections (admittedly due to the insight of the son, W.L. Bragg) to more easily come to the same result as the more intricate mathematical methods used by others in their work. The "Bragg Equation" is taught whenever 'diffraction' and 'diffraction patterns' are discussed.