IT is a long stretch of fruitful years, from Balboa's crossing in Darien to the completion of the transcontinental railways in the United States. Adequately to treat of Rocky Moun tain Exploration as a whole would require a series of bulky volumes. When, therefore, one is asked to tell of the multitude of ad venturous expeditions incident to the scalmg of the continental divide, within the limits of one small book, the task largely resolves itself into the recitation of a bead-roll of principal events.