The history of the origin and career of the two Slav States, Poland and Russia, is interesting not merely because it contains a vast number of surprising scenes and marvellous pictures of life, not merely because it gives us a kaleidoscope as it were of the acts of men, but because these acts in all their variety fall into groups which may be referred each to its proper source and origin, and each group contains facts that concern the most serious problems of history and political development.