Early in the autumn of 1867 my brother and I, with his family, were settled at St. Petersburg. I entered the university, and sat on the benches among young men, almost boys, much younger than myself. What I so longed for five years before was accomplished,-I could study; and, acting upon the idea that a thorough training in mathematics is the only solid basis for all subsequent work and thought, I joined the physico-mathematical faculty in its mathematical section. My brother entered the military academy for jurisprudence, whilst I entirely gave up military service, to the great dissatisfaction of my father, who hated the very sight of a civilian dress. We both had now to rely entirely upon ourselves. Study at the university and scientific work absorbed all my time for the next five years. A student of the mathematical faculty has, of course, very much to do, but my previous studies in higher mathematics permitted me to devote part of my time to geography; and, mo...