Because it is old. it has more worth, a better understanding
Answer:
serious/ mournful
Explanation:
as the passage suggests abraham lincoln 's speech was to dedicate a plot of land that would become Soldier's National Cemetery ,which is indeed serious and mournful because the land will become a place where people would mourn.
One can use allusion to achieve a well-rounded feel to their essay. You can reference to a multitude of other works to give your essay a more complex meaning.