memory is valuable ,this means if a person lose his memory about most important thing in his past life ,he seems to be tragic,therefor,if this happen to a nation, tragedy is the same outcome.Fortunately,human beings often retrospect to their histories with various ways.When two nice professors introdues the American history from revolution to Civil War,I think lecture is a effiency way for our foreigners restarting to get a correct recognition about how this country get everyting it owns today .I absolutely acknowledged that American people had done many greatest things in human's history with their bravery and wisdom,the Decleration of Independce as a great proof witnessed American people fighting for freedom and liberty.this's the eteral memory of American people,and also encourage other nations to build up their own new country,the French revolution just got impact from American revolution.