surmounted.” After citing expressions so gratifying, I must be permitted to subjoin the opinions I expressed regarding this great undertaking promoted by the Royal Geographical Society of London, in my Preface to the German edition of Robert Schomburgk’s Account of his Travels, published in 1841. “Immediately after my return from Mexico, I indicated the direction and the routes by which the unknown portion of the South American Continent between the sources of the Orinoco, the mountain chain of Pacaraima, and the sea-shore near Essequibo, might be explored. These wishes, so strongly expressed in the personal narrative of my journey, have at length, after the lapse of nearly half a century, been for the most part fulfilled. I rejoice that I have been spared to see so important an enlargement of our geographical knowledge; I rejoice too in seeing a courageous and well-conducted enterprise, requiring the most devoted perseverance, executed by a young man, to whom I feel bound no less by the ties of similarity of pursuits than those of country. These circumstances were alone able to overcome the aversion and disinclination which I entertain, perhaps unjustly, for introductory prefaces by a different hand than that of the author himself. But I could not resist the impulse of expressing thus publicly my sincere esteem for the accomplished traveller who, led on by the meritorious idea of penetrating from east to west, from the Valley of the Essequibo to Esmeralda, has succeeded, after five years of efforts and of sufferings (the extent of which I well appreciate from my own experience), in attaining the object of his ambition. Courage for the sudden accomplishment of a hazardous undertaking is easier to find, and implies less inward strength, than the resolution to endure with resignation long-continued physical sufferings, excited by absorbing mental interest; and still to press forward, undismayed by the certainty of having to retrace his steps under equally great privations and with enfeebled powers. Serenity of mind, which is almost the first requisite for an enterprise in inhospitable regions, a passionate love for any department of scientific labour (be it natural history, astronomy, hypsometrics, or magnetism), a pure feeling for the enjoyment which nature is capable of imparting, are elements which, when they combine together in one individual, ensure valuable results from a great and important journey.”