THE AUTHOR'S PREFACE

Summary

In the late evening of a varied and active life, I offer to the German public a work of which the undefined type has been present to my mind for almost half a century. Often the scheme has been relinquished as one which I could not hope to realise, but ever after being thus abandoned, it has been again, perhaps imprudently, resumed. In now presenting its fulfilment to my contemporaries, with that hesitation which a just diffidence of my own powers could not fail to inspire, I would willingly forget that writings long expected are usually least favourably received.

While the outward circumstances of my life, and an irresistible impulse to the acquisition of different kinds of knowledge, led me to occupy myself for many years, apparently exclusively, with separate branches of science,—descriptive botany, geology, chemistry, geographical determinations, and terrestrial magnetism, tending to render useful the extensive journeys in which I engaged,—I had still throughout a higher aim in view; I ever desired to discern physical phænomena in their widest mutual connection, and to comprehend Nature as a whole, animated and moved by inward forces. Intercourse with highly-gifted men had early led me to the conviction, that without earnest devotion to particular studies such attempts could be but vain and illusory.