After graduating from high school in Warsaw Jaczewski began his studies at the St. Petersburg Mining Institute, graduating in 1883. Following this, he worked in Irkutsk, taking part in an expedition to the summit of Mönkh Saridag and acting as an expert in to the gold mining industry in Transbaikal. He is credited with discovering and naming several glaciers, as well as making many geomorphological and meteorological observations. In addition to this he spent time studying the geology of the shores of Lake Khövsgöl in Mongolia.