Unfortunately, the journals and charts of Columbus are lost. But we have the full abstract of the journal of his first voyage, made by Las Casas, we have his letters and dispatches, and we have the map of his discoveries, except those made during his last voyage, drawn by his own pilot and draughtsman, Juan de la Cosa. We are thus able to obtain a sufficient insight into the system on which his exploring voyages were conducted, and into the sequence in which his discoveries followed each other. This is the point of view from which the labors of the Admiral are most interesting to geographers. The deficient means at the disposal of a navigator in the end of the fifteenth century increase the necessity for a long apprenticeship. It is much easier to become a navigator with the aid of modern instruments constructed with extreme accuracy, and with tables of logarithms, nautical almanacs, and admiralty charts. With ruder appliances Columbus and his contemporaries had to trust far more to their own personal skill and watchfulness, and to ways of handling and using such instruments as they possessed, which could only be acquired by constant practice and the experience of a lifetime. _Even then, an insight and ability which few men possess were required to make such a navigator as Columbus._ [Illustration: MAP OF ANTONIO DE HERRERA, THE HISTORIAN OF COLUMBUS. (See page 220.)] The first necessity for a pilot who conducts a ship across the ocean, when he is for many days out of sight of land, is the means of checking his dead reckoning by observations of the heavenly bodies. But in the days of Columbus such appliances were very defective, and, at times, altogether useless. There was an astrolabe adapted for use at sea by Martin Behaim, but it was very difficult to get a decent sight with it, and Vasco da Gama actually went on shore and rigged a triangle when he wanted to observe for latitude. If this was necessary, the instrument was useless as a guide across the pathless ocean. Columbus, of course, used it, but he seems to have relied more upon the old quadrant which he had used for long years before Behaim invented his adaption of the astrolabe. It was this instrument, the value of which received such warm testimony from Diogo Gomez, one of Prince Henry's navigators; and it was larger and easier to handle than the astrolabe. But the difficulty, as regards both these instruments,[49] was the necessity for keeping them perpendicular to the horizon when the observation is taken, in one case by means of a ring working freely, and in the other by a plummet line. The instruction of old Martin Cortes was to sit down with your back against the mainmast; but in reality the only man who obtained results of any use from such instruments was he who had been constantly working with them from early boyhood. In those days, far more than now, a good pilot had to be brought up at sea from his youth. Long habit could alone make up, to a partial extent, for defective