Physical crystallography before X-rays
Physical crystallography before X-rays describes how physical crystallography developed as a science up to the discovery of X-rays by Wilhelm Conrad Röntgen in 1895. In the period before X-rays, crystallography can be divided into three broad areas: geometrical crystallography culminating in the discovery of the 230 space groups in 1891–1894, chemical crystallography and physical crystallography.
Source: Wikipedia — Physical crystallography before X-rays (CC BY-SA 4.0)