Field work and techniques of observation at the IGY station at 2010 meters elevation on the Blue Glacier, Mount Olympus, western Washington State, are briefly described. The annual mass exchange on this glacier is large. Only very shallow penetration of subfreezing temperatures occurs, and the winter energy deficit is due almost entirely to increased ice mass. The 1958 ablation season, being long and hot, resulted in a specific mass deficit of 1.7 meters of water and a corresponding specific energy gain of 1.36×104 cal/cm2. During the 1958 melt season the principal sources of heat to the melting snow surface were, in order of importance, solar radiation, eddy conduction, and water vapor condensation. Of this heat, 64.4 percent was used for ice melt, and the remainder was lost to long-wave radiation cooling and heat of vaporization. Net water vapor transfer at the snow surface was small, but it played a measurable role in the over-all heat balance.