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The execution of the plan of the book is by no means: all that the author could desire To the elaboration of so vast an argument, the materials for which must be gleaned from every possible field of knowledge, the broadest and profoundest scholar might well devote the undistracted labor of a life time. To the writer, loaded with the cares of'a laborious executive office,'there were lacking both the leisure and the equipment otherwise attainable for so high a task. The best he could do was to turn one or two summer vacations into work-time and give the result'to the world. Of the correct ness of his position he has no doubt, and of the preparedness of the scientific world to accept it he is also confident.
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