The present volume has been completed precisely on the same lines as those that have preceded it; the only difference being in the addition of an index to the three supplementary volumes and of a supplementary index to this Preface. The necessities of printing have obliged me to construct two indexes in this manner, despite the plan being less convenient to the reader than that of one index only to the whole work. I have endeavoured to make the indexes true guides to all the points. I wished to bring into prominence in writing the volumes, as from their nature the matters to which any particular student would desire his attention to be drawn are necessarily over laden by, and partially hidden away under, much that is purely.
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