The study of glaciers may be divided into two branches: (1) the study of the physical properties of glacier ice, firn, and snow; (2) the investigation of the glacier's regime and its meteorological causes. The first branch comprises the thermal and crystallographic conditions of the ice, firn and snow of glaciers, and their transitional forms; also the plasticity, movement, erosion, etc. of glaciers. The second branch is concerned with quantitative determinations of accumulation, ablation and the total regime of glaciers, and with the meteorological causes affecting them. This second branch also includes the reactions of different types of glaciers to changes in their regime.