Translator's preface. There are three objectives in translation of works of this character: to give a faithful, literal translation of the author's statements; to give these in a manner which will interest the reader; and to preserve, so far as is possible the style of the original text. The task has been difficult in this work because, in using Latin, the author availed himself of a medium which has ceased to expand a thousand years before his subject had in many particulars come into being; in consequence he was in difficulties with a large number of ideasfor which there were no corresponding words in the vocabulary at his command, and instead of adopting into the text his native German terms, he coined several hundred Latin expressions to answer his needs.